My google fu is weak today.

My work is deploying a new application using MSSQL 2005 (SP1). On our database server we have a 36GB system drive, and a 220GB drive for SQL. When I logged on to the server yesterday it had 0 free space on the C: drive. After a reboot it was back to 26GB. As of right now there is 1.5MB free. Searching the drive shows nothing, ~6GB of files total (including the 2GB page file). SQL is installed to the D: drive, as well as all the databases.

So it appears that something is taking up hard drive space, and never releasing it. This is the first time I've ever worked with SQL2005, having only had experience with MYSQL on my personal webserver, so I am really in the dark. Has anyone ever seen this before? Any ideas? SQL related, or Windows?

Thanks in advance for all the help you guys can give!