This was an old family computer, now used exclusively by my parents. It's Windows XP SP2, with 256Mb of RAM. Recently running any process has become difficult, even loading thumbnails in explorer - which I've never seen occur before.
The computer has been slow for a few months, but I don't use it. I noticed, after a while, that the task manager had been disabled. I edited the registry to re-enable it and then tried a few things to see if they'd help, such as the windows error check, a defrag and an AVG scan. The AVG scan found viruses, trojan horses and tracking cookies. I used CCleaner to wipe the temporary files and whatnot to get rid of the cookies and AVG dealt with the other stuff. For some reason my parents had set NoScript to "Allow Scripts Globally", which I corrected. It took me long enough to get them to use firefox, heh.
I also began trawling the Add Or Remove Programs panel and My Documents to get rid of anything to free up space, and now the hard drive is about 50% empty. I then cut down the start up processes. Not sure if that'll help at all, but I thought I'd be thorough anyway. Still no improvement in terms of speed. I'll probably buy my father RAM for his birthday in June. As sad as that'll be, it might help a little.
Other than that the only other thing I can think of that might be causing problems is dust somehow reducing fan speed and making the CPU melt, but that's probably unlikely. If all else fails I may just open the case and blow on the inside
Does anyone know what I could do to further improve the speed of executing programs on the computer?