I'm An Idiot, And Probably Have Some Kinda Virus

So, lately I've randomly been having problems with programs not wanting to open (I get a window error message saying "Windows cannot access the specified device, path, or file. You may not have the appropriate permissions to access the item." At first it was just Fraps, so I tried uninstalling it and reinstalling it, which didn't work, but then I uninstalled again and reinstalled it to a different directory (it was C:\Fraps, and I changed it to C:\Program Files\Fraps), and it worked. However, now it's doing it with Photoshop, and screw trying to reinstall that... I don't even remember where my disc for it is. (Fraps takes like a few seconds to uninstall/reinstall, so I didn't care about doing that.)

In addition, now other problems are cropping up. A couple times now, I've gotten a message saying some kinda windows thing crashed, and a message along with it saying my computer will restart in 1 minute, which it then does. I noticed something suspicious in Task Manager (83583137:1587479803.exe), which won't close when I choose End Process, and when I click Open File Location, nothing comes up. That's when I figured it's prolly some kinda virus.

So, I tried to download/install AVG to run a scan. However, it gives me an error when I try to install every time I try. (The Windows Installer Service could not be accessed. This can occur if you are running Windows in safe mode, or if the Windows Installer is not correctly installed. Contact your support personnel for assistance.)

Any advice on how to fix this? ><