Microsoft doesn’t provide any way to disable Intellisense. This wouldn’t be a problem, except Intellisense can and does crash.
To disable Intellisense, close Visual Studio and navigate to your vcpackages folder:
C:\Program Files\Microsoft Visual Studio 8\VC\vcpackages
Rename the file feacp.dll to something like foulup.dll.
Now, if you actually miss Intellisense, go visit Whole Tomato Software.
Update: Visual Studio 2005 SP1 seems to have fixed the crashing issues.