This is a great disk BUT is not one of the latest "fluid dynamic bearing" drives from Maxtor so is not going to be as quiet as the FDB drive that may be in your existing box.
I use a 4G120J6 and can record about 70 hours on it. It can get quite hot in a Sky+ box so I tend to leave the top off the disk holder to allow more heat to escape. If you want to have an FDB drive in there you should use (I think this is the right number) 4K080K4, which is 80 gig and gives about 45 hours recording. It is difficult to get hold of in this country but search the 'net for German sites that can supply it.
Once a disk is fitted you will need to do two things: 1) Run "housekeeping" from the secret menu 2) slowly cycle the Sky+ box on and off a minimum of 10 times so that the Maxtor drive drops out of write/verify mode. They are normally set to do this for the first 10 or so power-ons and can cause a few problems when the drive is stretched (watching live pause and recording another channel). Once the write/verify is removed everything settles down.
The %age used/available indicator is shot to bits, but this causes no problems to the operation.
You will also need a special torx security bit to get into the box.
It's a ten minute job to swap the disk, just make certain you remove the power before "playing".
No problems to the disk have been caused by the recent software upgrade.