Make sure you're not holding down the Windows button?
While running a minimized game, shut down explorer.exe, (windows taskbar), and then try going back to the game, (via alt+tab, or task manager, if you use the switch to button).
I wouldn't bother try updating your DirectX - I can't think of any reason at all why that would be a problem, unless your drivers were somehow corrupted, but if your hardrive has that level of corruption, I don't think it matters anyways. What games are you trying to play? Have you tried playing an OGL game, like World of Goo? See if that works. If it does, that would confirm it's a problem with DirectX, even though it's probably not.
Try changing your desktop resolution to the resolution of the game, (if the game has a resolution of 1280x960, for example, change your desktop to that, and see if it still minamizes).
I'll just post some random quotes that worked for other people on teh internets, now:
Random Solutions #1 & #2 wrote:
I too had the same problem, but after a bit of searching I found the culprit for my case was Norton Internet Security. After disabling the ccApp.exe in the Windows task manager, my games ran fine. The downside to this is that it also disables your firewall and antivirus.
Another method that managed to remedy the problem (temporarily) was opening the nVidia control panel ---> 3D settings ---> adjust image settings with preview ---> switching to manual preference control then switching back to application controlled.
Random Solution #3 wrote:
Removing the Folding @ Home client fixed the problem for me.
Folding @ Home is a program automatically installed with ATI drivers, and maybe nVidia, as well.
Also, try disabling all background programs, (AIM, Steam, whatever, just make your computer run the bare basics. If stuff works, then you can start everything back up one by one and test to see which program it is). A few people in a forum had Skype, for some reason, being the problem, for example.
Try some of that, and if nothing helps, I can search some more. If Google doesn't eventually have the answer, you'll just have to reformat and see if that helps, lol.