Performance issue of Server 2012 VM on ESXi 5.1 U1

Performance issue of Server 2012 VM on ESXi 5.1 U1

I'm having issues with a VM, as stated in the topic, that runs on ESXi U1,
build 1065491. The machine is sluggish and i can't figure out why.. Here's
the details.
It runs on a Dell T420, has 12X1.9GHZ cpu's (it's a E5-2420). License is
vsphere essentials, so i'm limited to 8vpu per host. I got a few vm's, but
the cpu is not choked on the box it runs pretty smooth. All of the other
vm's are snappy.
I allocated 40gb of ram to the 2012 machine. I attached a few screenshots
of what i see in the vsphere client, nothing seems maxed out, the cpu in
the vm doesn't go that high, no disk IO problems in ressource monitor,
memory usage seems ok.. but god the vm is sluggish.
I'm installing microsoft exchange 2013 CU2 right now on it, i started the
install yesterday 3:00 PM, it' been 16 hours and it's not done. Installing
office 2010 took me about 1 hour also.
This vm is a production server, it's a small business email server. I got
to get this thing working in 2 hours.. at least i took a snapshot before i
started working on it yesterday, because i didn't trust the VM, it's so
slow.
Not so sure where to start, but hell if anyone could help in any way, i'd
be quite happy. If someone offering consulting services could remote on
this server here to find out wth is happening.. i'm open to any options..
Edit: I used hd speed to test the drive speed, and it's really
inconsistent on the 2012 VM, compared to a server 2003 vm i got here.. So
it might have to do with disk IO ? Not so sure.. Drives in the server are
600GO 15K SAS, 3 drives in raid5 on a H710 controller.
Thanks !!!!