Help! Windows PC's not booting! Also I cannot be more specific!

Hello. I have 4 PC's. An acer aspire one, two dell laptops, and an old dell desktop. The acer and the dell desktop are running windows 7 ultimate. The dell laptops are running windows xp and the other windows 7 pro(all of these are x86/32bit). Anyway so yesterday, the xp laptop gave black screen with a cursor when booted up(safe mode too), then the problem progressed tot the BSOD. We called Dell, booted it from a USB drive, and they said the HDD was corrupted. Then the other did the same thing this morning AKA right now. so far it is in stage 1, otherwise known as black screen with cursor. There were NO file transfers between the two(IE email attachments, FTPs, torrents, P2Ps, etc. ). I CANNOT afford for the Acer to do this as it has work and coding projects on it!

I have no idea what this is. Virus, malmaintainence, bug, etc or even if this "thingymajig" is eve taking out the entire hard disk as opposed to just the windows partition.
Hypothesis- worm/vrus/trojan spreading via LAN

oh and I am going to try file recvery via ubuntu live CD, then reformat and reinstall windows.

Download and burn to CD or write to flash stick Microsoft Standalone System Sweeper
boot it to run a full scan.

Then boot into the WIn7 DVD repair console to see if it offers a repair. If not run STartup Repair repeatedly. This should automate SFC but if not run it from Command Line in DVD System Recovery Options: SFC -SCANNOW Run in Command Prompt at Boot

You may be better off wiping the HD to clean reinstall Win7 as an infection this serious may linger and not be completely eradicated. Also the files can be copied out using Linux CD, Win7 DVD or Repair CD, or Paragon Rescue CD, however they should be quarantined on a disk, stick or external until scanned repeatedly with Malwarebytes.
Copy & Paste - in Windows Recovery Console