Help!!!

I have a Dell Latitude D610. Today, while working online, I got some sort of message that there was a problem with my computer and it suggested that I run a scan. Thinking it was my virus scan, I clicked it, only to find that I was lucky enough to get some sort of Impending Disaster on Your Hard Drive Virus and this was some kind of "trial version" for a PC fixer. I closed the window, but it was too late...then a bunch of "Warning, Warning, Will Robinson" windows popped up all over my screen, claiming the system could not operate. Then I got messages saying that the "media could not be loaded" and that "system had inadequate resources". The machine then suddenly shut itself down and restarted, and now all my icons and programs are gone...but that is not the worst part (I found out how to get them back)

I can't follow the process to get them back because NOW I get a Blue Screen of Death saying that I have an Unsurmountable Boot Error". I think this is totally related to the virus and that it has somehow damaged the boot program for windows.

I have no idea how to fix this..luckily, I have a fairly recent back up (that NEVER happens) but I do NOT have installation disks for this computer (got it used).

Short of buying a new hard drive, any options? The computer DOES boot, but about two minutes into using it, the blue screen appears. I removed and reseated the hard drive, but no luck.

This is my research computer, as well as my bookkeeping computer, so it is just inconvenient for me because now I have to actually take NOTES for my articles rather than just review the data on the other computer....and since my other computer is a netbook, I don't want to overload it with bookkeeping data....sooooo....HELP!!!