Unable to run certain applications

My computer suddenly refuses to run downloaded and installed applications. Specifically, I am having trouble with my instant messenger, but I attempted to download and install a few other simple programs to see if it was a general problem and sure enough, even though installation appears to work, nothing happens when I try to open the programs.
My computer will "think" for a few moments and act like maybe it's going to open, but nothing comes up.
The task manager processes tab says aim.exe is running, for example, but the program doesn't appear anywhere else, like in the system tray or in the first task manager tab (the one that tells which applications are running, right?).
I finally tried a system restore, but my computer said it can't do a system restore for some reason. This problem only began in the last few days. It is an hp tc1100 tablet pc running windows XP tablet edition...any ideas?

 

Is your anti virus up to date and have you done a scan recently.

 

Yes, I just updated and ran my antivirus and it didn't find anything wrong. My next step is to back everything up and completely reformat the computer, unless someone is struck with inspiration and figures out how to make this better!

 

A backup is allways a good idea but a reformat might be jumping the gun a bit. Have you tried running any malware removal programs eg. spybot & adaware

 

weird hmmm try to post a hijack this log to see if there is any virus your virus defintion didnt pick up

maybe too much ram are being taking up and if you got the cd you could try to put it in and start it up and click repair to that helps

and did you install a program before it stopped working

 

I am having a similar problem, I am running windows 98 and aol 8.0 optimized, Have mcAffee firewall, nd have down loaded other protections. Every thing was OK Saturday morning only my system icon/program was mising, the device tab was gone and cd's would not play utomatically, My son - in- law cleared my sys tay of all but two short cuts an now aol will start but the sign on screen will not let me use the setup buootn nd says it is searching for a modem then freeezes up, My solitaire screen will open and the cards will display then freezes, Help screen will not show help wording and the gray screen will stay on pressing alt-cntrl-delete will bring a blue screen with wirding -System is busy_ nd i have to Push Power to turn it off. He must have removed a partial of a program-- I have no recovery disc