When you open iTunes, does iTunes .exe appear on the processes tab and then disappear or does it persist?
Silent launch failure with iTunes.exe not appearing or disappearing quickly from the task manager has been associated with running the latest iTunes with an old version of Quicktime.
So if you haven't done so already make sure you have the latest versions of iTunes and Quicktime installed.
As a matter of interest to Quicktime and Safari work normally?
If an out of date Quciktime is not the answer, there is general advice on troubleshooting launch failure here:
http://support.apple.com/kb/TS1717
I would work through it, even if it doesn't help you will know if the problem is account specific or general.
It is also a good idea to make sure your PC is free of malware as that can cause launch failures.
Run a full scan with the free version of malwarebytes
http://www.malwarebytes.org/
You can also look in the Windows Even Viewer immediatly after trying to start iTunes to see if there is a helpful error message.
To open the event viewer:
Control Panel>>Administrative Tools>>Event Viewer
Or type Event Viewer into the search box.
Then select Windows Logs>>Application
Open the Event viewer immediately after iTunes crashes.
The error message should be at or near the top.
Double click on it to open more information and press copy.
Paste the result into your post.
You are looking for a message starting something like this:
Problem Event Name: APPCRASH
Application Name: iTunes.exe
Application Version: 10.2.1.1
Application Timestamp: 4d756476
Fault Module Name: iTunes.dll
