Who woulda known?

Hi, I recently got a new bass and a fender rumble amp (15W). I used a guitar cable that's about a year old and hasn't been used at all, really, to connect the two. After plugging it into an extension cord I noticed that i got a small electric shock where my arm touched the strings, and that also when i touched my computer I felt a kind of 'buzzing' feeling that you get when you touch ungrounded computers. So I knew something wasn't grounded and I plugged the amp directly into the socket. This seemed to solve the problem, but then I got another electric shock. I took the bass off the cable, and the amp began to make a kind of humming sound.

To me, it's obvious that some part of either the amp or the cable isn't grounded properly, as the humming stayed when I took the bass out of the equation and none of my other electronics have this problem. I live pretty far away from any kind of repair shop so I was wondering if you could give me some tips to find out whether it's the amp or the cable that has the problem? I have no other cables, unfortunately. And don't worry, I'm not playing anymore, I don't want to be a Darwin Award nominee.

Alright so basically I don't know how an amp works, i.e. whether it boosts the signal or just retransmits it at a louder power. What I wanted to ask is if an amp has a certain number of watts, does that mean it can give out a certain level of sound? Because if that's the case, then does that mean that if I broke the limiter on the volume control then I could play even really lightly picked notes really loudly and clearly? This is a hypothetical situation.

So basically I sat on my laptop and I heard a crunching sound, so I took the hard drive out. There were some loose pieces so I tried to hammer them into place and now the disk is in little pieces!

Apparently I can use a disk defragmenter to put the pieces back together but how can I download it on to the disk if I can't put it back in? And how do I use the defragmenter? Is there a button?