Search for Hidden or System Files

I had that problem lately...in fact I had it these couple of weeks, when my computer was working bad...
I took it to the comp fixer, and he told me, I had 3 Trojans and one worm, in System Hidden files!!(no antivirus could find it of course). It got in my Windows Register, and was ruining my Windows XP Home Edition every day...
Anyway, he said it was impossible to fix, so what do I have to do, crash my windows and install again...there was another problem yeah...my CD Windows Service Pack 2 was broken on one part, creating some files which were impossible to read...so all in all I was Fu**ed up...hell no I wasn't!! that guy, comp-fixer, installed new XP Professional, gave me the best antivirus, and now...erm...
I will tell you, how to search deeper in your comp and your hidden files, not to get your comp crushed...Ok this is the way:
By default, the Search companion does not search for hidden or system files. Because of this, you may be unable to find files, even though they exist on the drive.

To search for hidden or system files in Windows XP: 1. Click Start, click Search, click All files and folders, and then click More advanced options.
2. Click to select the Search system folders and Search hidden files and folders check boxes.
NOTE: You do not need to configure your computer to show hidden files in the Folder Options dialog box in Windows Explorer to find files with either the hidden or system attributes, but you need to configure your computer not to hide protected operating system files to find files with both the hidden and system attributes. Search Companion shares the Hide protected operating system files option (which hides files with both the system and hidden attributes) with the Folder Options dialog box Windows Explorer.

Also, it is useful to divide your computer in two parts: Particips; you can put ike 20 GB on Windows (that's C) and you can leave the rest on your programs and running softwares(local disc D). That's useful, cuz when your computer gets infected by virus(es) it is much easier to crush your windows down and reinstall it, since you don't lose anything.
Ok that were some interesting infos for your Comp security...scuse me if you find this post too big...
Cheers!