High memory usage on Virtual machine

Hello,

I have an issue with the memory usage of my virtual machines in that they are too high for no reason.

My Server has a Gigabyte MA78GM-S2H motherboard

                          AMD Phenom x4 Processor

                           4GB RAM (Kingston)

I Have 2 Virtual Machines(server 2003 and XP) each with 1 GB RAM.  Only to power them on they use 70% of their memory.If i ask them to do a simple defragmentation for example i get WARNINGS because the guest memory usage approaches 100% !! I let them on once and i got THE PURPLE SCREEN OF DEATH on my server screen !!

Also on my server screen,prior to the P.S.O.D.  under "to open esx server console type Alt F1..." i get in red : 0:00:04:38.182 cpu1 1074 APIC : 1470 APICID 0x01

I would be very gratefull if u could help me with my problem,

i would be glad to give any info u need the hardware/software i'm using if needed.

THX