My wife and I are going to share a PC,, W7,, can we have seperate iTunes accounts and libraries on the same PC?

Yes

Configure your PC for an addtional user account.

http://support.apple.com/kb/HT1495

Windows users:

Look in your computer's Help documentation to learn how to set up additional user accounts. To locate this information:

1. Click the Start Menu, and then click Help or Help and Support.
2. Enter "new user" in the Search field.
3. Press Return.

If you create multiple user accounts on one computer but want the same media to be available in iTunes for all users, see iTunes: How to share music between different accounts on a single computer.

Sorry for joining this discussion with a further question! I have posted a similar question. I av set up two user accounts for my wife and I. However how do avoid having to duplicate the music library in each users account if for example a CD is being ripped to one users library I cannot get it to automatically update in other library unless you duplicate (hence use up twice as much storage on PC).

Thanks!!