I don't know if this is a hardware or software problem, so I'm posting it here.
My Compaq Presario 1700 worked great until a couple of weeks ago, when it started alternating between normalcy and what I would call super-slow mode. For about 10 minutes at a time, the computer would operate at about 1% of its normal speed, and CPU usage in the Task Manager would drop to about 1%. While the computer was in super-slow mode, the hard drive would continue making noise, and occasionally would make a much louder "klunk" than normal.
Following the instructions of Compaq's online support people, I downloaded their hardware-diagnostic program, but it didn't catch any problems. I then went through all the standard "improving your system's performance" software stuff -- checking for errors on the hard disk, disabling visual themes, eliminating unnecessary start-up services, etc. -- but nothing helped.
Then yesterday, the problem got far worse. First, the computer stayed in super-slow mode for about 30 minutes. I tried restarting, but it continued in super-slow mode through the startup process, which of course took a really long time. Then it went back to normal. But the next time I tried starting up the computer, I got a blank screen after the Windows logo disappeared. The computer will launch properly if I force it into Safe Mode, but will not launch in normal mode. I've tried System Restore and "use last settings that worked," but that doesn't help.
What could the problem be? Could it be solved? Thanks.