I'm running Windows 7 on a Dell Studio 1535 laptop, normal midrange laptop specs. As of last night, whenever I start Windows, it makes it to the blue login screen at a normal pace, lets me enter my credentials, and then slows to a near-halt when I press login. If I wait a few minutes, it will make it to the desktop, at which point every single thing appears to happen at a glacial pace, forever. My computer continues to act like a 386 trying to run Windows 7 until I shut it off.
Task Manager, if I manage to open it and it stays open, doesn't show anything awry or any odd processes. Nothing unusual shows up in the Windows event log. I have almost nothing running at startup. My laptop's plugged in, the fan is running fine, I ran memtest and it came up fine. I have plenty of disk space. No peripherals are plugged in.
When I start in safe mode, I experience the same thing, except it's marginally more usable since safe mode is so lightweight. Still, exactly the same. Once in a while a program I open will just explode and throw up a "foo has stopped working" dialog, presumably due to the extreme lack of resources -- but what resources?
I have this Windows installation on a hard drive with Ubuntu on another partition, and I dual-boot them, but my setup in this regard has not changed for a while. It was still working fine last week after Tuesday Windows updates. I haven't done anything else strange that comes to mind.
Any ideas as to how to troubleshoot this that are easier than 'reinstall'?