What do you mean 'wont let me.,..'? What prompts are you seeing? What version of McAfee is installed?
Assuming home products are installed:
To check that double-click the taskbar icon to open SecurityCenter
I ask because it shouldn't be doing that, are you sure it isn't Windows 7 UAC protection that is causing it?
To temporarily turn off VirusScan is easy
Click Virus and Spyware Protection on the Home page
Click Real-Time Scanning
Click Turn Off and tell it for how long.
Also is this Windows 7 SP1?
You can also contact Technical Support staff by phone or online chat free by clicking the link under Useful Links at the top of this page.
That also could be the result of a fake alert type malware. Some stop you opening/running exe files. You haven't had any strange seemingly legit popups?
Why are You sure it cames from McAfee?