im guessing ur computer has been running for a while since the programs wont start. sounds to me that u hav fragmented files, right click ur HD go to properties>tools> and click Defragment now...
first analyze and see if a defragment is necessary. if so dreframent (be patient its gonna take a while) and then reboot.
if still the same thing pull out the RAM for 10 minutes (make sure the computer is unplugged from the wall) and then plug it back in after the 10min.
that happened to my old P3 and pulling out the RAM for couple minutes did the trick