Cant open any of the drives on hard disk..plz help

Hi

I am running McAfee Anti Virus on my system. There was some virus on the system that kept prompting the windows explorer to ask for internet access grant.
As per McAfee recommendation, I blocked the program.
After an update, McAfee shows me that some files in windows folder on C drive are trojans and can not be cleaned. As per the recommendtion I deleted some files and quarantined some.

After this, when i click on any of the drives in my computer, I am asked to chose the program to open the drive with..

Please suggest what should i DO?

Ankit