I had a single external USB drive connected to my laptop and it was assigned as drive F. I added an additional (portable) USB drive and it was originally drive H. Today I boot my PC without the portable drive attached and the original USB drive is now listed as H. If I plug the portable drive in it is recognized as drive F. Is there anyway I can reassign the drive letters?

Right click on MY computer
Select Management
God down and select Disk Management on the left
Then right click on each drive and rename as they want/will allow you too.
IT should remember it if windows does what it is supposed to

Thanks, got it back to normal.