imcdata directory in exchange server 5.5

The IMCDATA directory ( E:\exchsrvr\imcdata ) in the exchange server 5.5 is around 2.5 gig and my hard disk is about full.
1. Is there a way to clear this ? if so please give me the step by step instructions.

2. can the files in the directorybe deleted ?

3.Please give me few basic tips to maintain and administer the exchange server 5.5 .

Please reply

Regards

Joel