Windows Backup has not been set up. According to the Control Panel.
(First off and just to be clear, I use Vista and I'm guessing you probably use Win7 at least, but I believe the basic functionality and locations are the same.)
"Backup" and "System Restore" are both accessed via the "Backup and Restore Center" in the Control Panel, but they aren't the same thing. "Backups" aren't automatic, but system restore defaults to "on", and it can definitely use up
quite a lot of disk space unless you manually change the total it's allowed to use. (In Vista, you have to do it via the command line, in Win7 you may be able to do it via the GUI, but I don't know.)
Chkdsk may not do you much good since it will only find the lost space if it's being taken up by corrupt files (and if you have 4.4 GB of corrupt files, you definitely have a problem unrelated to simply uninstalling programs.)
Without knowing how much space was being taken up by various files/directories, including hidden and/or system ones, it's going to be a bit difficult to figure out where your 4.4 GB went, but you can use
TreeSize Free (run as administrator) to scan your system disk to look for unusually large folders/files. (You should "unhide" hidden files under folder options, if you normally keep them hidden.)
By way of reference, system restore points are stored under System Volume Information, in files with non-human-readable names like "{c42cf6af-474d-11e4-ba1d-00038a000015}{3808876b-c176-4e48-b7ae-04046e6cc752}". It's not the easiest thing to actually look into the restore points, but you can at least check the file properties for a time-stamp, to see if it corresponds to uninstalling your software.
