It's not possible with the home products. Using a manual "Custom" scan it is possible to exclude drives and to set it to scan "Program Files & Documents Only" but that is about as flexible as it gets.
My suggestion would be to move those to another drive or removable media and then switch off the automatic scan.
In Security Center v11 this is possible. However it appears you can't exclude specific files / folders from the real time scanning. You have to pick either i) All Files, or ii) Programs and Documents. It would be a big help if the real time scanning would also have per file / per folder exclusions.
Yes we have suggested it to McAfee. This is such an ancient thread the oriiginal poster will have to refresh his/her membership in order to respond..