Geoff - nice article, thanks for posting.
One thing I wanted to mention on security, if the account that SQL Agent runs with is denied access to run a command line script (CmdExec), a workaround would be to create a Proxy for CmdExec and then map an account that does have rights to run this job.
Although I have never tried this with SQL 2000, I have with 2005+ and the documentation seems to imply you can do it: http://support.microsoft.com/kb/890775
This keeps all security concerns happy because it elevates permissions to run the command line (VBScript in your case) only for a specific job or jobs.
Overall a very resourceful solution. I've been working on a "roll my own" solution to monitor several parameters of my servers through WMI hooks for some time now - disk free%, CPU Utilization, memory, I/O, etc. Who knows when I'll ever get it completed/tested but if I do I'll be sure to share!