Sorry to hear...
Alas, you are not alone in this.
I have watched in great dismay & horror over the past weeks, as more and more McAfee customers post their 2010 version update woes.
Here are just a few threads describing identical/similar problems:
There are many others, as well, generally being handled as "one-off" situations.
Many home users -- who take their McAfee updates silently -- may not even realize that their unbootable computers were rendered unusable by this update process.
While no 2 computer systems are the same, there is clearly a serious problem with the 2010 builds, esp on Dell systems with bundled McAfee products.
After reproducibly rendering my otherwise rock-stable computer unbootable except into basic safe mode, not once, but twice, and after damaging my OS to the point of necessitatiing restoration to the factory image, my solution was to completely uninstall McAfee ASAP once the factory image was restored, and to install another security suite which is performing beautifully.
Despite truly valiant assistance from the volunteer mods and a few McAfee folks here at the boards, no one at the corporate level (i.e. engineering, tech support, software development) showed either interest or aptitude in attempting to diagnose or resolve the problem.
Given the millions of $$$ McAfee pays to Dell for exclusive rights to bundle their products on Dell computers, I found this wholly unacceptable.
I have had many computers over the years, 98 to XP to Vista to Win7/32 to Win7/64, and have NEVER, EVER experienced anything like this.
2 weeks into the debacle, I am just now barely back to "normal".
The lost time and effort and productivity and sleep have cost me enormously.
Unless you have countless hours to spare, an expendable computer, and more expertise than I do, my advice -- sadly -- is to do as I did.
Quite frankly, even if McAfee could correct the problem, my trust has been so completely destroyed I could never go back.
That said, I do hope you are able to somehow recover the use of your computer, since I know how terrible this experience is!
Need to add that I am running XP Professional
Need to add that I am running XP Professional SP3. Otherwise, nothing fancy!