External HDD to Internal?

I recently bought a 2TB HDD and have been using it in an external enclosure, but now I want to move this hdd to inside my case. I was just wondering if there is anything I need to do to prepare the drive. I wish to keep all the data that is on it.

I currently have it runniong as A:/ drive. If I install it inside my case will it still show up as A:?

Also, I have a older 500GB drive running as my primary disk, and have noticed in the Windows Experience rating thingy, that it rates everything on my computer either 7.7 or 7.9 but HDD data transfer only gets a 5.9.
Is this because the drive is a little old, or am I using a slow sata port/cable?
I don't know a lot about sata, so if my question is dumb I apologize, but I'm sure I read that my motherboard has 3.0 Gbps and 6.0 Gbps sata ports. Or maybe I'm getting confused with USB 3.0? :confused Help!?!

 

bump

 

Check withh your USB HD manufacturer as some will not connect/work outside of the enclosure. ie you may not be able to take out of enclosure and install into your Rig.

 

It's not a factory built external hdd. It's an internal 3.5" which I have put in to a usb external enclosure.
The issue is not the physical installation, I want to know if the drive will still appear as the A: drive when I connect it directly to the motherboard via sata instead of usb.
Thanks for replying

 

No normally the allocated Letter will be the next one on as to what you have installed HD's/Roms having said that IF you have no Floppy allocated you can manuallly designate the letter ''A'' to that drive via Disk Management.