A required iTunes component is not installed. Please repair or reintall iTunes. (-42404)

Plausibly, that's a damaged SC Info folder, sarah.

Try the XP instructions from the following document:

iTunes: Missing folder or incorrect permissions may prevent authorization

Does that fix up the trouble?

Drat.

If iTunes actually opens after that message, could you post some minimal diagnostics for us, please?

In iTunes, go "Help > Run Diagnostics". Uncheck all four boxes, as per the following screenshot:

... and click "Next".

When you get through to the final screen:

... click the "Copy to Clipboard" button and paste the diagnostics into a reply here.

(Fingers crossed, the list of installed components may give us some clue as to what iTunes thinks is missing.)

🙂 Perfect, thanks!

Fairplay is missing. It usually shows up between QuickTime and Apple Application Support.

The most common cause of that is damaged program files/folders relating to Fairplay (or CoreFP) on your system. So, in order to clear those away, I'd try the following document:

Removing and Reinstalling iTunes, QuickTime, and other software components for Windows XP

Does that get rid of the message, sarah?

I'm having the same problem at the moment and I'm so upset about it 😟

Microsoft Windows Vista Home Basic Edition Service Pack 2 (Build 6002)

Hewlett-Packard Compaq Presario B1200

iTunes 10.4.1.10

QuickTime 7.7

Apple Application Support 2.0.1

iPod Updater Library 10.0d2

CD Driver 2.2.0.1

CD Driver DLL 2.1.1.1

Apple Mobile Device 3.4.1.2

Apple Mobile Device Driver 1.57.0.0

Bonjour 3.0.0.2 (333.2)

Gracenote SDK 1.9.1.485

Gracenote MusicID 1.9.1.102

Gracenote Submit 1.9.1.133

Gracenote DSP 1.9.1.43

iTunes Serial Number 001AB60802FFF0C8

Current user is not an administrator.

The current local date and time is 2011-09-06 13:42:17.

iTunes is not running in safe mode.

WebKit accelerated compositing is enabled.

HDCP is not supported.

Core Media is supported.

Video Display Information

Intel Corporation, Mobile Intel(R) 965 Express Chipset Family

Intel Corporation, Mobile Intel(R) 965 Express Chipset Family

**** External Plug-ins Information ****

No external plug-ins installed.

iPodService 10.4.1.10 is currently running.

iTunesHelper 10.4.1.10 is currently running.

Apple Mobile Device service 3.3.0.0 is currently running.

I am having the same problem. I am running iTunes 10 on Windows Vista and I have an iPhone 4. I have uninstalled iTunes and Quicktime, run ccleaner, reinstalled iTunes, and I still get the problem. The iPhone shows up in My Computer, but not in iTunes. Here is the diagnostics report:

Microsoft Windows Vista x64 x64 Home Premium Edition Service Pack 2 (Build 6002)

TOSHIBA Satellite M305

iTunes 10.5.1.42

QuickTime not available

Apple Application Support 2.1.5

iPod Updater Library 10.0d2

CD Driver 2.2.0.1

CD Driver DLL 2.1.1.1

Apple Mobile Device 4.0.0.97

Apple Mobile Device Driver 1.57.0.0

Bonjour 3.0.0.10 (333.10)

Gracenote SDK 1.9.5.502

Gracenote MusicID 1.9.5.115

Gracenote Submit 1.9.5.143

Gracenote DSP 1.9.5.45

iTunes Serial Number 0035B29403A4A0A0

Current user is not an administrator.

The current local date and time is 2011-11-18 07:21:51.

iTunes is not running in safe mode.

WebKit accelerated compositing is enabled.

HDCP is not supported.

Core Media is supported.

Video Display Information

Intel Corporation, Mobile Intel(R) 4 Series Express Chipset Family

Intel Corporation, Mobile Intel(R) 4 Series Express Chipset Family

**** External Plug-ins Information ****

Plug-in Name: Aeon

Plug-in Loaded: Yes

Plug-in Version: 0.9.1

Plug-in File Version: Unknown

Plug-in Path: C:\Program Files (x86)\iTunes\Plug-ins\vis_Aeon.dll

**** Network Connectivity Tests ****

Network Adapter Information

Adapter Name: {B6BB589C-1E99-42D1-818E-FADC88A66B4D}

Description: Intel(R) Wireless WiFi Link 5100

IP Address: 192.168.1.120

Subnet Mask: 255.255.255.0

Default Gateway: 192.168.1.1

DHCP Enabled: Yes

DHCP Server: 192.168.1.1

Lease Obtained: Fri Nov 18 06:46:41 2011

Lease Expires: Sat Nov 19 06:46:41 2011

DNS Servers: 192.168.15.1

Adapter Name: {CDBD518E-7A32-4E0C-AD60-95A9F16E0242}

Description: Marvell Yukon 88E8040T PCI-E Fast Ethernet Controller

IP Address: 0.0.0.0

Subnet Mask: 0.0.0.0

Default Gateway: 0.0.0.0

DHCP Enabled: Yes

DHCP Server:

Lease Obtained: Wed Dec 31 16:00:00 1969

Lease Expires: Wed Dec 31 16:00:00 1969

DNS Servers:

Active Connection: LAN Connection

Connected: Yes

Online: Yes

Using Modem: No

Using LAN: Yes

Using Proxy: No

SSL 3.0 Support: Enabled

TLS 1.0 Support: Enabled

Firewall Information

Windows Firewall is on.

iTunes is NOT enabled in Windows Firewall.

Connection attempt to Apple web site was successful.

Connection attempt to browsing iTunes Store was successful.

Connection attempt to purchasing from iTunes Store was successful.

Connection attempt to iPhone activation server was successful.

Connection attempt to firmware update server was successful.

Connection attempt to Gracenote server was successful.

Last successful iTunes Store access was 2011-11-18 07:04:02.

**** CD/DVD Drive Tests ****

LowerFilters: PxHlpa64 (2.0.0.0),

UpperFilters: GEARAspiWDM (2.2.0.1),

D: TSSTcorp CDDVDW TS-L633P, Rev TO01

Audio CD in drive.

Found 9 songs on CD, playing time 76:28 on Audio CD.

Track 1, start time 00:02:00

Track 2, start time 06:58:26

Track 3, start time 21:04:12

Track 4, start time 28:07:33

Track 5, start time 43:38:05

Track 6, start time 47:09:07

Track 7, start time 49:35:63

Track 8, start time 59:49:68

Track 9, start time 68:08:56

Audio CD reading succeeded.

Get drive speed succeeded.

The drive CDR speeds are: 24.

The drive CDRW speeds are: 24.

The drive DVDR speeds are: 24.

The drive DVDRW speeds are: 24.

**** Device Connectivity Tests ****

iPodService 10.5.1.42 (x64) is currently running.

iTunesHelper 10.5.1.42 is currently running.

Apple Mobile Device service 3.3.0.0 is currently running.

Universal Serial Bus Controllers:

Intel(R) ICH9 Family USB Universal Host Controller - 2934. Device is working properly.

Intel(R) ICH9 Family USB Universal Host Controller - 2935. Device is working properly.

Intel(R) ICH9 Family USB Universal Host Controller - 2936. Device is working properly.

Intel(R) ICH9 Family USB Universal Host Controller - 2937. Device is working properly.

Intel(R) ICH9 Family USB Universal Host Controller - 2938. Device is working properly.

Intel(R) ICH9 Family USB Universal Host Controller - 2939. Device is working properly.

Intel(R) ICH9 Family USB2 Enhanced Host Controller - 293A. Device is working properly.

Intel(R) ICH9 Family USB2 Enhanced Host Controller - 293C. Device is working properly.

FireWire (IEEE 1394) Host Controllers:

OHCI Compliant IEEE 1394 Host Controller. Device is working properly.

Most Recent Devices Not Currently Connected:

iPod nano (3rd Generation) running firmware version 1.1.3

Serial Number: 6U742DHGYXT

iPhone 4 (GSM) running firmware version 5.0.1

Serial Number: 870224UDA4T

**** Device Sync Tests ****

No iPod, iPhone, or iPad found.

Update: The software told me I needed to restore my iPhone to its factory settings. So I did that. Now it says it cannot write to the iPhone when I attempt to synch it.

So now my iPhone is set to its original factory settings and I cannot restore any of my data to it.

After I updated iTunes to the latest version, that's EXACTLY what happened to mine! So now I have an iPod touch with no music or apps because the "sync failed to start".

Okay, after visiting the Geniuses for a couple hours and getting nowhere, I went home and worked on it for another day. Here is the solution: Uninstall every last scrap of Apple software on your computer. That means iTunes, Safari, Bonjour, ABSOLUTELY EVERYTHING ever made by Apple - including any support applications you find while scrolling through the list of software available to uninstall when you are in Control Panel. Get it ALL off. Then run CCleaner to clean out any temporary files and clean your registry. Defrag too if you want. Then reboot. Then reinstall a fresh download of the latest version of iTunes. You can then restore your last backup of your device and everything should work fine. Then you can reinstall whatever Apple software you need.