Electric Shock

Unfortunately, our entire house is not properly grounded. We only have a Hot and a Neutral wire on our house wiring. My iMac is located upstairs on a different outlet than the PC, and it does not give off any small electric shocks when I touch its ports. I just went back downstairs where the PC is, and I touched the ports with it turned off, then I turned it on and received a slight shock. I was able to keep my finger on it though without any pain. After this recent event of getting a little shock, I remembered that about a year ago the sound cable on the back of the computer gave me a little shock. One day it stopped giving me a shock and then went back to doing it again. Seems kind of strange doesn't it? The computer runs just fine despite this little problem. The monitor never messes up, and I don't receive any errors. I just plugged in one of my Flash Drives to the PC where it shocks me and the drive was recognized without any problems. Could this just be normal for these ports to give off a slight electric jolt or is there something really seriously wrong?

The sound cable is not USB. It is just a regular sound cable. I'll have to try the computer on a different outlet to see if that changes anything. This computer is not very old. The shocks don't seem to damage it at all; I'll just have to keep messing with it and see what I can do with it.

Thanks.

A friend of mine re-wired the plug the computer is connected to about 2 years ago. The polarity that I know of is correct, but next time I see my friend I'm going to ask him to check this problem out. He knows quite a bit about electricity. The house not being grounded is a problem that needs fixed, but this is a project that is too big to take on at once.

I'm going to mark this question as answered because your replies basically tell me what the problem could be. I thank you all for that. It is possible that I could be imagining this. Sometimes I feel like I'm getting shocked by something metal, touch it again and I don't feel anything. Seems strange. Could be just that the computer is building up static somehow and holding it until the computer is shut off. I don't feel like I'm in much danger considering that I've had the computer for 2 years and have never had any major problem with it. Since getting my Mac, I only use the PC every once in a while. I'll use it even less when I install Windows XP on my iMac. To me this is just a little project that my friend and I will have to work on. If he comes over soon, I'll have him test it and see what he thinks. I'll try to remember to post a new reply of what his verdict is if he comes over shortly.

Thanks.