RDM access fm Xp Pro VM

Hello,
I have a ML110 G5 with esx1 5.1 I wanted to add a 2 TB disk and I followed the instruction of the link:

http://blog.davidwarburton.net/2010/10/25/rdm-mapping-of-local-sata-storage-for-esxi/

Everythink was ok. I added the  disk to a fresh created VM (Xp Pro).
It takes 30 sec. to boot without the RDM and almost 10 minutes with RDM !
Any help to discover what is the problem ?
Thank you

Bob