external hard drives missing

Ok I got a prob and don't know a lot about PC's
My old laptop caugth fire but some nice guys I know managed to get some doc's off the old hareddrive onto a freecom external drive. Got a new laptop and just hooked up external drive. Computer (vista) recognised it and off we went. Great sorted. then They got the old hard drive (xp) and put it in a hard drive caddy (mad dog mega vault 2.5) that I got in the states. They tested it on their PC and it worked fine. Put it on my PC and it does not recognise it at all. If is as if nothing is connected does not show up in the my computer section or anything now the freecom one that was working fine doesn't show up either. They both have power as the light s go on.

Help Please
thanks
Anne

Maybe you can check it out using the disk management
Click Start > Run and type diskmgmt.msc in the Open: line and click OK. The Disk Management snap-in will open.

See if the disk is showing up there and if so assign a drive letter to it.
Or maybe your USB port may not be working
Can you try another port.

They both have power as the light s go on.

Click to expand...

But not necessarily enough power. Are you using an external power supply with both USB drives? Your USB ports may not provide sufficient current to use them simultaneously.

no disk showing up but in device manager there doesn't seem to be anything with errors. It worked fine before with no extra power but tried it both ways. Any more suggestions?

i have a similar problem with external usb driver but get around it by switching it on and off also check if caddy from the usa can be used on 230v 50hz power as their power is 110v 60hz although this does sound unlikely as you had it running allready you could also try to connect the drive directly to the computer by unpluging the dvd/cd drive and connecting the hard drive in its place you may have to change the jumper at the back of the drive to the slave position

OHHH sounds complicated think I will bring it to someone.