If I still had the code available, I would share...

We had a dilapidated 200 box that would not delete the old backup files on an external drive... Needless to say it would fill up and we would puke on a regular basis if someone did not manually traverse Win Explorer and delete the old backups.

After learning about the xp_FixedDrives procedure (here, by the way), I created a sproc ( triggered by an agent job firing hourly) that would check our drive and if we got below a comfortable free space level, it would automatically email the network administrator.

After we had some baseline data we were able to track our average usage on an hourly and daily basis. As more and better data came in, the procedure was altered so that if it was predicted to drop below the comfort zone before the next working shift, it would let the admin know before the end of the working day. This saved many early morning messages telling us that the backup dropped us below our established comfort zone

Another element that this brought to the table was the ability to track the variations in daily usage. We are primarily a web design and host company, so peoples working schedules can be seen minutely when looking at the various file sizes... No surprises then when a blizzard closes 95% of businesses that the logs increased in size