Ms. Compy Fix-It Needs Help

My issue: Windows 7 computer (for work) often stalls when I’m typing. I can continue to type even though I don’t see anything showing up, and a couple of seconds later it catches up. Sometimes when this is happening, my web browser (Firefox, updated) goes non-responsive for a few seconds, then clears up. Occasionally, it will crash entirely. Other problems include when I’m working on a PowerPoint presentation, I will be doing a non-difficult task, like changing the colour of a bar on a chart, and it will freeze. Sometimes it will crash my program; other times it just takes a while.

I have 3GB of RAM, have a decent-sized paging file, and have run multiple diagnostics tests on it. I reduced my number of anti-virus programs so only one is running at a time (Avast is running, and I have McAfee, SpyBot, and MalwareBytes installed). I have done an msconfig and unchecked all non-Microsoft programs to run at Startup, and I still have the same problem.

I am at the point where I have to look away from the screen as I’m typing, because I don’t see my words coming up and don’t want to wait every few seconds for it to catch up. Seriously, it happens every few seconds.

Any advice?