No "Boot from C" error - Laptop - XP

Hello,
I am running XP Professional on a Laptop 2.0 GHtz (Compaq I think)....512 memory. We leave this running 24/7 and it doesn't hibernate but have the monitor go off after 10 minutes (the typical laptop setting).

Anyway, during the past month or so, when we hit the "on' button which usually wakes the computer up, we get a bios screen saying that it can't find the hard drive. We do see A, D, and C and if we arrow up to C, nothing happens. The solution we've been using is to pull out the battery, pull out the plug, wait 10 seconds or so - put it back in, hit the power button and it will allow us to boot to safe mode (with networking) - once there, we do a restore to yesterday or the day before (whatever is bolded) and it DOES boot and restores properly.

It will stay that way for a day or two and then it will start again. At once of the restore incidences, as I was watching, it said "it was missing files" and "file was restored" messages - but it doesn't always do that.

I do have the original XP CD for this system but hate to do a total reinstall as I'll lose all of my laptop settings. (they're a pain to reinstall). What file is corrupted, the boot sector?. Why then AFTER I restore and it runs for another day or two, does it happen again? It seems like if you restore, the boot sector should copy over itself.

We have 2 laptops and a desktop (all running XP Pro). I am seriously thinking about getting new computers but only thing offered today is Vista..... any suggestions on Version of vista, if it's worth it, etc..... don't know what the solution is. Today's technology has changed so much. I noticed that IF I go with Dell, they offer a ton of space on-line that you can back up your drive.... I don't know - any help would be appreciated on suggestions of what to get. I'm NOT a gamer but am a heavy user of MS Office.....and like the latest and greatest.