External HD suddenly not detected

I have a 40GB BUSlink 2.0 external HD, which I've always been able to hook up to my MacBook Pro without any problems. In preparation for installing Snow Leopard (upgrading from 10.5.8) I thought I would use the BUSlink to back up all my files. I was using Time Machine (for the first time) and it told me I had to reformat the external drive before I could back up my files on it. So I did that, but it got stuck in "erasing" mode for more than 6 hours. I knew that it shouldn't be taking that long because I only had 4 or 5 GBs on the drive. So I restarted my computer and the external HD several times, but it was no longer able to detect the external HD. It's showing up in disk utility, but not on my desktop. I can't access it at all. I'm sure I've done something really idiotic. How can I get my Mac to detect the drive again?

Can you select the external in Disk Utility, select and erase and format from Disk utility. Probably not formatted is why you are unable to see it.

harryb2448 said:

Can you select the external in Disk Utility, select and erase and format from Disk utility. Probably not formatted is why you are unable to see it.

Click to expand...

Yes, I can select it from Disk Utility. I'm just not sure what to do next. I hit the "erase" tab, but what do I select from the "Volume Format" dropdown box? I'm afraid I'm going to inadvertently erase my Mac HD:

Mac OS Extended (Journaled)
Mac OS Extended
Mac OS Extended (Case-sensitive, journaled)
Mac OS Extended (Case-sensitive)
MS-DOS (FAT)

I have no idea what any of these mean

Mac OS Extended (Journalled) and Apple Partition Map.

harryb2448 said:

Mac OS Extended (Journalled) and Apple Partition Map.

Click to expand...

it has been "creating partition map" for 45 minutes now. is this supposed to be a long process?

wolverine04 said:

it has been "creating partition map" for 45 minutes now. is this supposed to be a long process?

Click to expand...

No. It should have created the partition map instantly and then completed the format. I suspect your 40 GB BUSLink hard drive has seen better days. Might be time for a new drive. Your first clue that the drive was having problems is when the erase was going on for 6 hours.

Regards.

chscag said:

No. It should have created the partition map instantly and then completed the format. I suspect your 40 GB BUSLink hard drive has seen better days. Might be time for a new drive. Your first clue that the drive was having problems is when the erase was going on for 6 hours.

Regards.

Click to expand...

but it was working fine before I tried to reformat it. It's also working fine on my PC, so how can the drive be bad?