Windows Vista Boot issues and incredibly slow operation

This just started suddenly, rather than a case of the computer gathering cobwebs (literal and otherwise) and slowly getting draggier and draggier. Suddenly everything became incredibly, incredibly slow, like, taking five or ten or fifteen minutes to start up Chrome, or load Excel, or do anything in any program. Nothing in particular seemed to trigger it - it just went from fine to incredibly terrible. The only thing it was doing at the time was downloading Tivo files from the Tivo box.

I shut it down and rebooted. It wouldn't boot. It went through its entire startup process normally and without until the point where Windows would normally appear with a login screen, and then it flashed a blue screen so fast I couldn't read anything on it, and returned to the beginning of the boot process. When given the choice to start in either normal or safe mode or last known good configuration, it doesn't matter what I choose, the same thing happens: a quick blue screen and return to the beginning.

I have once already booted from the Windows CD and used Startup Repair (which took a VERY long time to even load let alone finish the repairs.) It appeared to work at first. After repairs were complete it booted up normally. However, it still ran as slowly as before. I decided to let it sit for about 45 minutes to see what would happen. After that, it ran normally - for about 15 minutes. Then it went back to running VERY slowly. Programs take forever to start, webpages take forever to load. I decided to shut it down again. That took even longer. It worked through the shutdown process for about an hour - yes, an hour - before I got fed up and turned it off with the power button. It seemed to get stuck on the "Shutting Down" screen, which would've been the last thing it showed before shutting down if it had done so normally.

When I tried to start it again, it went back to the boot problems as above. So now it's running Startup Repair again. I might get a result from that in 45-60 minutes or so, if last time is any indication. I've tried pulling each of the memory sticks (there are two 1GB RAM sticks) but that didn't change anything about the boot process.

Suggestions?

 

Right now, for whatever reason, the computer is running fine and has been since the startup repair was completed last night. Gonna give it today and see what happens when I boot it up again tomorrow. I've downloaded and burned the Seatools file and if the boot process tomorrow goes bad again I'll give it a shot. Or is it worth doing regardless? I'd hate for there to be a hard drive problem, I just put this drive in brand new six months ago.

 

If you get a Dell Error Code 2000-0142. That's one of the classic dell HDD failure codes.