I use a script very similar to this on SQL Server 2000. The documentation on xp_fixeddrives and xp_smtp_sendmail can be found using a simple Google search. I run the script once a day and send myself an email telling me the amount of space free. I also run the script about every hour using a second job. This time it only sends an email if a drive is below a threshold and it sends a copy to the network admin as well.