Not an easy problem to find the solution for just with words..but I wouldn't hold out too much hope that the drive is any good any more.
The good news should be that it should have come with a minimum of 6 months guarantee so the equipment should be replaced, even if the data on it can't be.
If it was just not working on the computer then it might have been a fixable problem, the fact it no longer works on two different devices while the power still appears to be on is not a good sign at all.
However, just before for return it it might be worth while reading this site
http://pcsupport.about.com/od/toolsofth ... atools.htm
and downloading one of the Seagate tools they talk about.
As you say that you are not very technically competent then SeaTools for Windows sounds the easier thing to try. My only feeling is that in some cases it could actually be a problem with Windows & the disk which maybe this program would also suffer from.
The SeaTools for DOS would certainly give more clues as to an issue & would also still work even if the issue was with Windows - thus maybe presenting ways of solving it.
The nagging doubts is that it no longer works on the TV either which does not suggest that it will be a simple matter to fix.