Keystroke misses

I'm hoping I can get some help with a problem .... I've got a Dell desktop (about 4 years old). I didn't like the original keyboard, so I have switched it out a couple times before. About 6 months ago, I tried a wireless keyboard/mouse, but found it would occassionally miss keys that I know I typed. I tried changing batteries (often!) which sometimes lessened the problem but did not resolve. Lacking any other solution, I assumed it was the wireless setup and I replaced it with a new USB keyboard ... but this one is doing the same thing! I don't have this issue with my laptop or keyboard at work, so it's something odd with this computer. I gave my original keyboard away, so can' go back to it.

I'm also getting some other odd error messages peiodically, so I wonder if this keystroke issue is a symptom of something else. I've run some diagnostic tests (primarily Norton utilities) and nothing has resolve the keystroke issue. Although I've been around computers a while, I'm not a techie, so am out of ideas.

Any suggestions?

Thanks!
Linda