Windows cannot access the specified device, path or file....

I need some serious help please. As of last night, i've been receiving this error when attempting to open certain executable programs.

"Windows cannot access the specified device, path or file. You may not have the appropriate permission to run this file".

I'm running Windows XP Service Pack 3. I have 29GB of Space on my hard drive. I only use one hard drive, but because I had problems in the past, I had to re-install windows and have 3 backup's on my hard drive (That I CANNOT remove - always gives me some error of a file in use - cannot delete, but that's something entirely different (but if you have time i'd love to know how to clear).

Anyways this problem started last night. I wanted to delete online armor because its resource hungry, so I decided to download and install both PC Firewall and Antivirus as one of the programs suggested by this site. I wasn't using any anti-virus at the time.

When I downloaded and installed both, they gave me some type of error saying that the program needs to close, reboot the computer and if it persists call tech support.....?

The program cannot be deleted from my hard drive. The firewall was removed, but the AV says "Cannot delete PCTAVshellextension.dll: Access is Denied.

When I right click any program, the "run safer" option is there with the little symbol of the program but when I click it, it does nothing.

I can't find anything related in processes. I have all processes that load on startup controlled (i think) using ccleaner startup feature.

On top of all this....I can't System Restore! It always comes up incomplete saying that it didn't work. I checked the event viewer and it came up a bunch of errors but I don't understand them.

Some programs start, some don't. I tried googling this and there are at least 20 threads about the same thing but they seem to all start from different sources.

This all began IMMEDIATELY after installing the PC firewall/antivirus programs, which by the way gave an error on install saying to reboot the pc.

I run as administrator and i've tried enabling things via other threads, disabling IE security config (which doesn't exist under my remove/add components).

I'm seriously lost here. I almost want to format my hard drive but I have pictures of my son on there I don't want to lose, as well as World of Warcraft I don't want to reinstall (takes a day).

Please Help! :confused

It all began immedietely after downloading/installing PC firewall/AV.

If i'm omitting anything critical please let me know so I can help you help me. rolleyes

Thanks alot, you guys are great at what you do.