Sometimes threads load slowly because of net congestion. If your computer is sometimes fast and sometimes slow, the problem is your connection, not the 'puter.

I can get to my defrag program by clicking on the Start button, then Programs, Accessories, System Tools, Disk Defragmenter. The program itself, which I can double click on to the the same effect, is here: C:\WINDOWS\DEFRAG.EXE

"Defrag" (defragmentization)... well, the easiest explanation is it organizes your hard drive, taking all the data that's strewn haphazardly all over the place and putting it away in an orderly fashion. The computer I used to have at work would get bogged down, and it helped a lot to run defrag. Warning: the program can take a long time to finish.

On my current computer, I have to close everything by hitting CTRL/ALT/DELETE and "End Task" until I get rid of all the icons on the task bar. (I'm probably doing this the wrong way, but I don't know the right one.) This can get tricky, and I hope you don't have to do it if you try to defrag, but you'll at least have to temporarily disable your anti-virus software.