Well, I would have thought that your PC loaded with Windows XP would have found the approriate driver, but maybe it's because your phone is a motorola knock off and XP isn't able to recognize it exactly.
If the friend you mentioned is able to plug your phone into their PC, using your cable, and everything works...then that tells me it's just a driver issue.
In that case, if they have the motorola software disk they loaded on their PC, see if you can borrow it and load the driver software on your PC. If they didn't load any additional software then check the properties when your cell phone is plugged into their computer to see what the file name is of the driver, then you should be able to copy it to your PC.
You may need to delete any software drivers you had already added, or fall back to a restore point prior to you loading the drivers that didn't work.