Problem 1: There is no appropriate type for XenServer, only "Vmware server" with VMware icon.
Problem 2: As well as VMware ESX, XenServers are also discovered like Linux.
Here devicetester output for 3 different XenServer versions (only relevant entries, if you need full output please let me know):
Citrix XenServer 5.5.0 Update 2 Dell OEM Edition (Version 5.5.0-25727p-01)
HTTP title: Citrix XenServer Dell Express Edition 5.5.0
...
Description: Linux v21 2.6.18-128.1.6.el5.xs5.5.0.505.1024xen #1 SMP Mon Nov 16 09:08:33 EST 2009 i686
Kernel: Linux
Release: 2.6.18-128.1.6.el5.xs5.5.0.505.1024xen
Version: #1 SMP Mon Nov 16 09:08:33 EST 2009
...
ObjectID: 1.3.6.1.4.1.8072.3.2.10
Citrix XenServer 5.5.0 Update 2 (Version 5.5.0-25727p)
Description:
Kernel: Linux
Release: 2.6.18-128.1.6.el5.xs5.5.0.505.1024xen
Version: #1 SMP Mon Nov 16 09:08:33 EST 2009
Citrix XenServer 5.5.0 (Version 5.5.0-15119p)
Description:
Kernel: Linux
Release: 2.6.18-128.1.6.el5.xs5.5.0.496.1012xen
Version: #1 SMP Fri May 29 07:35:00 EDT 2009
