USB drive not showing up

I'm helping someone with a problem. He's just re-installed his system after it wouldn't recognise DVDs. He now has the latest updated 10.4. He backed up all his content onto a lacie mobile disk 320gb, newly bought for the purpose.System profiler shows its plugged in, Disk utility seems to see it as a Hitachi HD but the word Disk 1 is greyed out. The Finder invites him to initialise the disk which I've told him not to, of course. Any ideas why his iMac won't mount the external? Thanks from me, and if I can get it sorted over the phone, from him!
Tony3ts

Does disk utility allow him to run repair disk as an option

I'll check with him. If it does, can he do this safely, without losing his data? The External appeared before he did the system install, and he backed-up his data successfully apparently. Thanks for your help so far... Tony3ts

Hate to say it, but harddrives tend to often fail within the first few days of buying them... could be a bum drive.

Did he erase & install, or archive & install? (i.e. is his data still on the internal drive?)