Crawling THAT slowly indicates that something is seriously adrift.
All the above advice looks sound, although to me "wipe and reinstall" is the copout solution: it doesn't identify the cause of the problem, so when it happens again you're back where you started. I'd rather fix it and not reinstall.
Press Ctrl + Shift + Esc all at once. That will start the Task Manager.
If it's not already on the "Processes" tab, click Processes and then click on "CPU" so that the biggest number is at the top (click it again if it isn't).
Look to see what's using lots of CPU. If "System idle" is 70% or more, then click "Memory" and see what are the top users. Anything using more than 150MB is a hog.