I bought a Maxtor 120gb hard drive and I am trying to upgrade right now. There was a hard drive cable in the Maxtor box and I am wondering if I can use it as a replacement for the hard drive cable that was already in the xbox?

you can but its not in your benifit in any way.

many say that a new higher speed ATA IDE cable will help, i tried one (cause i had a few extra bucks lying around, now im broke PS: if you want to donate some money to a worthy cause pm me ) anyways, i tried one and didnt notice to much of a difference, it certainly wasnt worth the time or money.

Those cables are rated for transfer speeds, though. You can usually see on the cable what it is. I think the stock one in the box is like ATA 33, and the ones that come new are like ATA100 or 133.

I've run some tests on xbox's side by side, copying files using xcommander which shows a status bar of the copy. Obviously a new harddrive copies much faster, and with a new cable there is a slight increase in speed as well.

The main advantage to all this is faster game load times.