First thing I'd say to do is check which version of windows XP you really have.

click start. Right click my computer, and select properties. Under the general tab, what version of windows do you have?

Fresh UI can work wonders on tweaking a system but if used incorrectly it can cause major issues.

Turning on the file protection could cause some of the problems that you are experiencing. I am not too sure.

Sometimes windows file protection needs to be disabled to install certain programs. With it turned on, you can never install the software.

If you are worried someone is fiddling with your PC, I recommend you to install windows by yourself. It is not a complex procedure. We have a guide on our frontpage:

http://www.techzonez.com/modules.php...ion=show&id=15

I'd print that 19 page install guide out, and give it a try. The guide originally came from Paul Thurrott's Supersite:

http://www.winsupersite.com

With your own install you can rest assured that your installation is not tampered with. That said, it could be that a virus has crept into your system and caused these problems. YOu could have a hacker in your system as well, if you are not using a firewall.

http://www.firewallguide.com/software.htm

Try that for a good firewall.