Drive Letter Changer is a free portable tool which allows you to reassign PC drive letters in two or three clicks.
The program is small (a single executable under 400KB) and has a very basic interface: mostly just a table with a list of your current drive letters, their labels and names.
Click a drive you'd like to reassign, and a context menu appears immediately. (Maybe this is a bug, with a left-click being treated like a right? We're not sure.) Hovering your mouse over "Change drive letter" displays a list of possible drive letters, and all you have to do is click one.
Drive Letter Changer also supports the creation of volume mount points, where essentially an empty folder on an NTFS drive can point to another volume. If you'd like an easier way to access your drive E, for example, you might create a desktop folder SpareDrive, select E: in Drive Letter Changer, click "Mount in empty NTFS drive" and select Desktop\SpareDrive. Now, whenever you browse to SpareDrive, you'll see and be able to access all your drive E: files and folders. (An "Unmount" option turns this mapping off when you're done.)
There are also a very few small extras here. Click a drive and you'll find convenient options to open it in Explorer, or view its properties. Experts may also appreciate a Tools menu with options to launch the Disk Management applet, run the mountvol.exe command or restart Windows Explorer.
While this mostly works well, Drive Letter Changer has one notable problem: it doesn't appear to recognise network drives. Their drive letters are displayed as "free" in the program, and you can assign drives there, but they may not be accessible. This isn't a big issue - if you accidentally point a drive to the wrong letter, just reassign it - but it's still annoying. Hopefully it'll be addressed soon.