Huge log file on simple database that has transaction rolling back.

Hi, 

Have a database in "simple" mode which now has a 52GB log and has filled the disk.  The log space was used by a huge transaction which the developer has killed off.  The spid for the process now shows  as "KILLED/ROLLBACK" but the IO is going up a lot and log_reuse_wait_desc is shows ACTIVE_TRANSACTION. 

I can't shrink this log back to it's normal size because of the reuse wait and I'm wondering if it will be able to rollback with no space on the disk.  The disk has 10MB of space and there's nothing else I can move. 

Any ideas? 

Thanks