time machine drive not mounting

[maclisa]

Hi-

This is my first question at macosx.com. I am fairly knowledgeable so don't be afraid to challenge me. Here's my problem:

I have a MacPro 2x2.66 GHz Dual-Core Intel Xeon with 3gig RAM. I have a drive in each bay as follows:

1-500gig startup running Leopard 10.5.7
2-250gig drive old startup and has Tiger (10.4.11 i think)
3-500gig will use for boot camp eventually (only installed yesterday)
4-terabyte was used for time machine

the terabyte stopped mounting when i moved it from bay 3 to bay 4. i did get unable to read error when i restarted my computer asking to format, ignore or eject. i chose ignore the first time and went into disk utility where drive did not show at all. the next time i chose format then disk utility showed drive as "media" and now will not allow me to reformat, repair, verify, partition or anything.

since the drive was only used for time machine, i have not lost any "real" data. i can temporarily use bay 3 for time machine since that drive is new. i would however like to just reformat the bay 4 drive and use again as my time machine drive. the drive is less than 6 months old so i can return it if need be.

open to any suggestions even using command line to reformat

thank you!!!

lisa