Why external hard drive not showing up in my computer?

My 320 GB Seagate external hard drive is detected but not showing up in my computer. What should I do?

In disk management it shows up as 'unallocated'. If I initialize it, will I lose all data on the drive? It had 4 partitions.

In Device Manager it gets detected.

In cmd> diskpart> list volume it does not show up.

In My Computer also it does not show up.

Even BIOS recognizes it.

What to do? I don't want to lose any data on the drive. If I initialize it in device manager will I lose data?

I was installing window XP on my computer, usually I remove the external drive but this time I did not. The external drive was shown as 4 drives in partition manager during installation. But the installation failed. The next time I was installing windows again, the external drive was shown as 1 single unknown or unrecognized drive. I'm not sure if it was unknown or unrecognized. I'm sure I didn't format it. So what I need to do now? I don't want to lose any data.