You probably need to install the newest version of iTunes, version 9.0.2, which can be downloaded directed from the Apple site here: Apple - iTunes - Download
There are two different versions: one for the 32-bit version, and one that requires the 64-bit installer (this link is provided from the download page listed above). You will need to know which version of Windows 7 you have.
The 64-bit version of iTunes 9.0.2 works well on our Windows 7 computer. However, we have had problems with it auto syncing to our 8 GB iPod. Any time we attempt to auto sync, iTunes will go just so far and then Windows will crash. We have had to set iTunes to manually sync to the iPod now, transferring about 100 songs at a time in order to avoid a BSOD.
On its own (without the iPod connected), however, this version of iTunes works well. It connected to the Apple Store and validated our account without any problems and remains open playing music without issues.
I have done some research and found that it may be a power issue with Win 7. By default Windows is now not set to "high performance" in order to be more energy efficient, and since iTunes is such a memory-intensive program, this may
have something to do with the Windows crashes.