Moving Page Caching

I have an Exchange 2003 server. Following the 1.5x memory rule I have allowed 6GB of page caching. However my C drive is only 20GB in size, after time it is now getting full. About 2GB remaining. I want to move the page caching off the C drive. I currently have a single set RAID 5 in three partitions. (C: OS, E: Exchange, S: Support) Currently the caching is all on C: I was thinking of moving 4GB to the support and keeping 2GB on C.

Any thought recommendations as if this should done this way or not?