dsmonitor-192.zip (Works perfectly on all Windows platforms from Windows 2000 and up, both 32-bit and 64-bit, works perfectly in Windows 7) [updated June
16th 20th 2008, fixed some issues if the added drive is a CD/DVD-ROM, added lame cool icons, will be publishing source code soon sometime] 
Here’s another little program I wrote. It’s a tool that sits on the system tray and monitors the free space on the hard drives you specify (it works over network, too). I think it’s pretty useful when downloading a lot of stuff so you know the space will run out in six hours meaning you should do some housekeeping before going to bed. Or, you can monitor your HTPC remotely so there’s always free space for recording TV shows.
If DSMonitor notices the free disk space is under the limit you have specified, it can either show that on the tray icon (), display a popup or execute a program (so you can even send email).
Basically, it’s one of those programs I wrote pretty much for my own needs so contact me if you think something would make it more usable for you. This also means it’s not very pretty and the most convenient to use. At least it’s under 30 kilobytes in size.
Double click on dsmonitor.exe and it will appear on the system tray. Click on the tray icon and a popup will open with info about the paths you have added to dsmonitor.ini. See the included readme for detailed info. However, here’s a quick example:
settings monitor path "C:" # this will simply add C: to the list end monitor path "D:" alert type POPUP threshold 100MB message "D: will be full really soon!" delay 30min end # this will add D: to the list and alert you every 30 minutes # if there's under 100 megabytes of free space # NOTE: you can add more alert sections here! end monitor path "E:" removable # see the manual, but use this if the path is not always available # i.e. it's a removable drive or an unreliable network path alert type POPUP threshold 100MB message "E: will be almost full in 30 minutes!" time 30min once end # same as the settings for D: but with prediction # and the popup will pop up only once end end