This was probably cuased by a faulty Windows application causing Macafee to install badly and exacerbating the problem. Certainly, you've got some damaged Windows files. Repairs are easy assuming you have your original Windows install disc, but less so if all you have is one of those wretched OEM reinstallation CDs. However, let's try:
1. Boot in Safe mode (F8) during bootup. This will sometimes repair damaged software and all will be well.
2. In normal mode, run SFC /scannow with the install CD in the primary drive.
3. Reboot with the CD still in the PC and chose the option to repair.