Generally, it's not recommended to tweak your services. Even if you'd get it working now, it doesn't mean it will stay that way. Leave that to the pros.
McAfee is tightly integrated with the operating system, so it's not strange that this causes problems.
Disabling services generally frees up very little RAM or CPU usage. Especially compared to that total protection thing !
But if you want to do it anyway, try MSCONFIG, by enabling certain services you may find out which ones are necesary.
I'm not sure if there is any use in disabling services. Another choice is setting them to manual (as opposed to automatic), which would mean the services run only if/when nessecary.
If it turns out that what you've been doing has permanently corrupted your installation, you can uninstall with the MCPR tool and reinstall.