Not sure whats up with yours, but I had a similar issue (no other bootcamp or partitions on mine though). My Macbook Pro 2010 I attempted a clean install from a USB made ML disc. Started the upgrade, then it failed. I then could not install Snow Leopard/ Lion / Mountain Lion, kept getting error. Submitted report to Apple, I have yet to hear back from them.
My savior was that I installed ML onto a USB device, making it bootable. I then used Carbon Copy Cloner after booting into my ML USB boot drive, and cloned it to my internal drive. Worked fine afterwards. If you have a spare USB drive, you can try doing that. Its a good habit to make bootable back ups of your drive if you have a USB hard drive.
You say you have a partition on your hard drive - is this a bootcamp partition? If it is I would reformat your hard drive, removing your bootcamp partition.
It seems that a few people who tried to do a clean install of Lion when it was released, while leaving their bootcamp partition in place, experienced similar(ish) problems. Do a search on google for more information.
FWIW - I did a clean install of ML on my 2007 MBP last night and it works like a charm - it only took around an hour. Always backup or make a clone.
Wifi? there have been problems - and fixes. I assume that is the only thing that could take so long (though download an OS why should it take longer than downloading three full length movies from iTunes Store? it shouldn't)
Clean? just clone your system or make sure you have a good backup (or two) and with the actual install process - not the download which is separate issue - it can go like light-ning on an SSD in minutes. And Setup Assistant? nice good way to start off.
I would say there is no way to know if your system will run better or not or if it takes longer in the end, or just 'safer' and more stable method to get ML installed.
And you do want to save the installer so you can avoid downloading another 4GB later.
Free space or lack thereof is one factor, or maybe it is time for an SSD or new hard drive; swapping out the hard drive before it fails or checking to see if spare blocks have been used is best indication of likely or impending drive issue.
There are guides how best to put Lion/ML on 8GB USB and using Disk-Maker
How to make a bootable Mountain Lion install drive
Making sure your disk drive does not have any errors can only be done by spending time and effort and scanning for media errors or having a program that will - and a new OS is a good enough time for that.
OS X Lion: Unable to download OS X Lion wirelessly from Mac App Store - "Your device or computer could not be verified"
Mac App Store, OS X Lion
When attempting to purchase or download OS X Lion from the Mac App Store wirelessly with your Apple ID account, you may receive a dialog stating "Your Device or computer could not be verified. Contact support for assistance." This could happen when upgrading Mac OS X v10.6.6, 10.6.7, or 10.6.8 to OS X Lion via a Wi-Fi connection.
Use the following steps to delete your network preferences.
Important: You must be logged in as an administrator.
- Click the Finder icon in the Dock.
- Choose Go to Folder from the Go menu.
- Type /Library/Preferences/SystemConfiguration
- Copy the file networkinterfaces.plist to the desktop (to make a precautionary backup).
- Delete the file "networkinterfaces.plist." from SystemConfiguration.
- Restart your Mac.
- Create new location in Network preferences, in System Preferences.
- Choose System Preferences from the Apple menu.
- Choose Network from the View menu.
- From the Location pop-up menu, choose "New Location".
- Type a name for your location and click OK.
- Click the Apply Now at the bottom right to accept the changes.
If your network connection requires any special settings, you will need to enter them again.
Once you have made these changes, you should be able to connect to the Internet, open App Store, and try your OS X Lion purchase or download again.
Additional InformationThis issue may occur if your Mac's Ethernet port is damaged or inoperable, even if you aren't using Ethernet to try to download Lion.