Doesn't seem to actually load

I double click on the doom3 shortcut/exe/icon, and my system task manager says it is running, but in the taskbar and on my screen the only thing that happens is a massive slowdown in the CPU, and that's it. I already uninstalled, and then reinstalled it. So what's going on?

Have to tried right-clicking it in task-manager and clicking "switch to"? Hardly a long term solution but it would be interesting to see if that worked. I wouldn't bet on it though. Other than that, I cant really think of anythign else except the standard "make sure your patches/directx/drivers are up to date" speech.

Erm, should have been more specific. It shows up in the Processes menu, but not in the Applications, so I can't just "switch to..." because the splash screen shows up, goes away, program doesn't even seem to load but doom3.exe is in the Processes menu hogging up CPU energy until I end it.

I had this problem as well and apparently, in my case, it was the copy protection. I'd say, either try with a different drive, or use a no-cd crack.