is this a virus

I recently downloaded McAfee and various Microsoft Updates on my home computer.  Days after doing this I started having trouble with booting up my computer.  The whole thing seems to have died. 

I've gotten Windows to come up just barely but then it crashes.  I've gotten error messages such as NDLTR is missing (or something to that effect) and something about inserting a boot diskette in A.  I also had error messages saying something about dumping physical memory.  At one point the blue screen said you might have a virus. 

But I can't even get the system up to run the virus software.  I don't think it was setup correctly in the first place.  I fear that I've lost all my data.

Any ideas?