Unmountable_Boot_Volume, fixed - bad sector/hd? --- now what?

How old is the drive? if it isn't all that old, you should check the S.M.A.R.T. health status of the drive. The easiest utility I know of that can check this is SpeedFan. If everything checks out, you could try to do a reformat and clean install.

You haven't been doing anything strange like reformatting under Linux, and then go back to Windows? That's the only time I've seen odd boot sector problems that were not due to a dying or damaged drive.

We bought the computer in 2001 and the hdrive was replaced 13 months later...I guess that makes it about 7 years old, give or take. Is that considered old?

I have not been doing anything weird like reformatting under Linux and going back - that is WAY over my head! My kids were away for a month and the computer was powered down until just the other day when they returned home....and viola, the blue screen.

I'll find the SpeedFan utility online and download for use, so thank you for that tip. A couple of questions:
-Do you know if there is a link to instructions on a clean install I can reference?
-will the clean install wipe the drive and lose my data? IF so, I spose I;ll need to back up & then move it back over...


Based upon the hard drive age, is it likely that I have a deeper problem with the hard drive...or should I just roll the dice and let it go?

thnx

7 years can be pretty old, though it really depends on how much of its lifetime it has spent on and in use, how full it has been, and even how often it was defragged over the years (It is possible to defrag too much, but you would probably need to have severe OCD to do it). The Speedfan free utility has a nifty little reporting feature that will be able to compare your HD model's metrics with identical ones in service and give you an idea for the relative age of your drive.

As for a clean install reference, not too difficult, but I don't know of any detailed walkthroughs to assist you. If you can't find one through Tom's Hardware, I'd try searching blogs like maximumpc.com or lifehacker.com Might have to do some digging there, but both those sites write "How-to's" very well.

You will need to do a data backup with a clean install. You are pretty well covered as long as you copy the contents of every Users' profile on the system. Depending on how much music, pictures, games, files, etc everyone has, this can take up quite a lot of space so plan accordingly. Programs like Microsoft Office, Firefox, etc. will all need to be re-installed, so if you use any licensed software on your computer, make sure you have all the product keys for them.

Bottom line is if this drive even gives the slightest hint of trouble during the analysis, replace it. Not sure how large of a drive you have, but given what you've said about it, you could find a replacement drive online that is 5x the capacity well under $100. If you don't need that much storage, just figure out which drive has the best price/GB ratio and go with that, though it'll probably be close to 1TB.

Do the usual memory and cpu stability tests.