Ok more help required
Had new drive in all working, backup up all me data to it, everything fine.
I then went about and removed the old os drive so I could use the 120 gig as an os instead and leave the new 200 gig one as storage.
I swopped the leads around last night, press the on button, the computer fired up the fans, I heard the hard drive kick in then it shut itself straight back off. I then had to remove the power cord for a bit then plug it back in, press on button and the same thing happened.
I unplugged the power lead from the new 200 gig and the system boots up fine but as soon as I reconnect it and power up it shuts itself straight back down.
I thought ah ferked Harddrive with all me presious data on, I then went to bed and tried to convice myself it had been all a dream.
Got up this morning and found it was not a dream so I tried the new 200 gig in the system upstairs, the computer fired up and loaded fine allowing me to view the data. I tested the drive and used it for a couple of hours in that system with no problems so I put it back in the main system and get the same problem, machine will not power up with that drive connected, it did when I first installed it but won't now.... any ideads please.....