Get disk space percentage free with SQL Server 2005? I am currently using SQL Server 2005 and (undocumented I believe) master..xp_fixeddrives to get free space on my database volumes as part of my monitoring.

However, this only gives me an absolute number of MB free. What I really need is percentage free.

Is there another way in SQL Server 2005 to get this? If not, is there some other light-weight way to get it? If I can, I want to avoid installing a Java JRE, or Perl, or Python on my database server. Perhaps vbscript, or a small Windows executable on the file system?

Yes, I know I can Google this, and I have. It looks like there are a few ways to accomplish it, and I'm curious how my DBA brethren have handled this.
This can be done through PowerShell.  See the below:

Get-PSDrive |
    Where-Object {$_.Provider -like "*FileSystem"} |
    Select-Object Name, Used, Free, @{Name = "Used_Percent"; expression = {$_.Used / ($_.Used + $_.Free) * 100}}


Or, through WMI:

Get-WmiObject -Class Win32_LogicalDisk |
    Select-Object DeviceID, VolumeName, @{Name = "Used_Percent"; expression = {($_.Size - $_.FreeSpace) / $_.Size * 100}}


Please see Aaron's comment to your question.  I completely agree with him, this is not something that is easily done through SQL Server.  You can finagle this to be run within SQL Server, but it's not necessarily a native way to get this information directly from SQL Server.