[markem]

There is a tool for moving from XP to Win7. I recommend win7 for the new security features and performance enhancements.

Note that blowing away a partition table does not mean that the data is gone or not recoverable. Any viruses, in the boot block for example, will still be there.

I would suggest that once you have deleted the drive, you use CCleaner in its most secure setting to erase everything, well, everything that isn't in a bad sector/block. You will also need to remove the boot block, probably by hand.