The only REAL way of being safe is to WIPE your hide drive and then do a Windows recovery or reinstall.
The problem is that if you just delete a file in Windows it stays on the hard disk so can be easily recovered.
And anyway, Windows keeps all sorts of secret files and hidden files that most of us dont even know about that you can never REALLY know a hard disk is clear of personal data unless you ZAP it.
So your first plan of action is to make sure you have a recovery CD so you can reinstall Windows after you have zapped the hard disk.
If you DO have a recovery CD then download DBAN from here
http://www.dban.org/
Make a DBAN "boot" CD and then boot from that CD and get it to do its business. DBAN will write over the hard disk with all sorts of rubbish over and over again until there is no chance of recovering any files.
This will delete any recovery partition on the disk so make sure any recovery CD you have is a full Windows recovery CD.
When that has finished then use your Windows recovery CD to reinstall Windows.
May sound a lot but it is the only way to be certain you have removed all your personal data.