This will be really stupid, almost certainly power related but before I make my office even more messy I thought I would check I haven't overlooked something simple.

I have pulled an IDE HDD (WD400 Caviar) from a clients machine after it was causing 0xED UNMOUNTABLE_BOOT_VOLUME BSOD. I replaced the HDD and installed windows but now I need to perform data recovery on this drive. When the drive is connected to the original machine it spins up fine, the Windows logo appears followed by BSOD so it is functional and read by the BIOS. If I use that machine to boot to live XP then the HDD is recognised in disk management as healthy and active but the file format is not recognised so I cannot access it as an external drive.

The above is fine and as expected, the problem is I have taken the drive back to my office to work on it but when connected to my external IDE caddy it will not spin up even though it is powered by mains. If I connect it to an old P4 machine I have here it will not spin up, if I just connect the molex from a new Antec 350W PSU I have here the drive will not spin up (no IDE ribbon connected at this point because the mobo does not have IDE). There are no jumpers on the drive so it is set as single or master.

Any ideas as to why it won't power up? I though perhaps my P4 machine wasn't providing enough juice but the Antec PSU and the caddy should provide enough. I tried the caddy on-site which failed, to check the drive was still functional I connected it to the original PC again and it powered up so I am assuming the drive is still fully functional.

Cheers