Keyboard letter jump

Hello,

This is March 2012. I read all the prior reports from years back about the cursor location
jumping around the page. Same problem on my HP Compaq. Has not always been a problem, just last few months. Had the computer purged and cleaned of all trash and not needed files and registry errors. Cannot fix, still jumps, mostly on letter "t" and "s". Deleted keyboard and mouse driver, re-installed, no help.