HI!
First, you should know that these LOG files are not like IIS or other text log files that contain history, but these files are actualy the transcations (the actual messages that Exchange receives/sends/delete/move/etc - the data).
These files are then commited to the *.EDB database files.
The files are normaly left on disk until the backup program backs up the databases then deletes them.
This behaviour can be changed - you can enable "Circular Logging" where the server delete each LOG file once it is commited.
This saves disk space on expence of fault tolerance, so it is generaly not recomended.
If you are in disk space emergency, sort these files by date and move all expect from the recent ones to drive D.
Also in emergency you can change NT swap file from system properties to something like 200mb , reboot the server, gain some space and time to work with less presure, and then do whatever.
Disable the memory dump anyway from System Properties if you're already there...
Now back to Exchange specific stuff:
First - Check whats going with your backup program,
and ofcourse create a full backup (including databases and brick level).
Second - you can dictate to Exchange where you want the log files to be - in your case you can place them on D if you have more space there (and short on C).
You can use Exchange Administrator (I think its clicking on the server and Properties), or you can use Exchange Optimizer. I think it's easier from the Exchange Administrator.
You can take the opertunity and buy new hard disk for the server (better 2 in mirror), and place the log files there.
This can improve both performance and fault tolerance (and did I mention disk space) and is the best solution with thinking ahead.
This is also the best cost-effective solution, instead of playing with low disk space.
3rd - Implementing a good policy like configuring outlook to clean "Deleted Items" on exit, using "Auto-Archive" or other solutions, and educating users not to send large un-needed files to everyone, can help keep a reasonable database size. You'll see it's importance not only when disk space is low, but also when Exchange starts crashing and you have to bring it up again.
That's for now.
Bye
Yizhar
Yizhar Hurwitz