Change of key behaviour in Windows 7

My computer is fairly new and very powerful. I use it for Finale, a music notation program, and windows office apps. I can be typing away in Word or Finale when the keyboard keys suddenly acquire new functions. For example, pressing 'e' might open Windows Explorer. Pressing 'O' might cause the program to minimise. The only way I've found to get out of this is to reboot (the computer). Driving me mad - can anyone help please?

Hi have you tried another keyboard?

Hi Oscer1, thanks for quick reply. It's a good thought which I can try if pressed, but at the moment I don't have another keyboard.

For now use the onscreen keyboard to see if same problem happens. But would be nice to test another keyboard. When using the onscreen keyboard unplug the external one so it don't interfere

Thanks - I'll try that next time it happens.

Work through the Troubleshooting Steps for Windows 7
starting with all checks for infection/spyware, SFC, Clean Boot, then go back to top and work through the rest.

Gregrocker - thanks for the thought. I'll try that first thing tomorrow

Gregrocker - I took the steps you suggested, and some issues were certainly found, so thanks for that. I'll now use the system today as usual - if the fault doesn't recur I'll post it as 'solved' and thank you again!

Folks - I've now had the problem recur, and I've done some other tests which might help someone help me!
- performance with on-screen keyboard is identical
- here's a list of mis-performing keys on this occasion (other times, there have been other effects, though some are consistent)
-- pressing 'L' (upper or lower case) locks the system
-- space bar minimises the window
-- down arrow gives a smaller window, or minimises a small one
-- up arrow maximises a smaller window
-- left arrow makes the window smaller; subsequent presses move the window across the screen
-- right arrow similar to left arrow