Manual update of DAT file for McAfee

Hi,

I have been having a problem with the malware that

blocks system restore
prevents security and microsoft updates
blocks access to security websites
redirects google search
does not allow the installation of any new security software (such as Trojan Remover Malwarebytes) even from the safe mode

I am a paying customer of McAfee - - for the last time! They have been completely uncooperative in resolving this issue that their service should have prevented.

I am thinking if I can download the most current updates (DAT files) on my laptop and manually install them on my desktop so then a resulting scan should be able to find and remove the problem. Does that sound too logical?

So is there anyone that can help me with a step-by-step on how to manually install the McAfee updates (DATs)? Any assistance is greatly appreciated!