Windows 7 - Virtual drive letters: Deassign/reassign seemingly important ones?

Got a brand new PC with way more bells & whistles than I'd expected. I'm the sort that assigns a LOT of virtual drive letters. Some are mapped network locations, but most are SUBSTed to folders I use often. The new PC has assigned drives E thru H, which are letters I'd prefer to use for my own purposes, to:

SD/mini-MMC/RS (drive E)
CF/MD (drive F)
SM/xD (drive G)
MS/Pro/Duo (drive H)

I understand I might want to use these later in life, but for now I'd like to reclaim them. Is there a way to do that? And if there is, will there be a way to *undo* it later? Thanks so much for any help.

Mark

As long as you have not installed programs that may need to refer to those devices you should be OK.

Control Panel/Admin Tools/Computer Management/Storage/Disk Management. You can change drive letters in there.

Drive Letter - Add, Change, or Remove in Windows 7

Thank you for the quick and helpful reply, HD.