Vista - Slow performance in VM

Hi,

I'm using Virtual Server 2005 Version on a powerful newly built server (16GB
RAM and SAS disks), the version of Virtual Server is: 1.1.629.0 EE R2 SP1 and
all virtual machines have Virtual Machine Additions version: 13.820
insatlled.

My problem is that one of the 2 virtual machines is running really slow on
anything it does for the first time, then the second time the action is
performed its quick. Looking at the performance counters it appears to be
down to the disk as the Avg. Disk Queue length and Avg. Disk Read % counters
are very high.

The VM has been configued for SCSI disk use.

The second virtual machine which is running along side has no issues, and is
configred exactly the same - same OS - Windows 2003 R2 SP2, same parititons,
NICs, RAM allocation etc.

The affected VM has been like this since it was first installed, but has
since been put to use in a production environment as once everything has been
ran, it runs quickly.

I've checked the disks for errors, but everything is ok, drives dont need
defragging. Does anyone know what may be happening here, any ideas to speed
up the VM?

Marcus