Xen is free to download and use, just a license from Citrix is required (free as well, just request and install).
Works fine for 2 of 3 servers, the last one still "Linux". This is only Xen server where:
1. snmp is active (not configured however)
2. Xen OEM Dell edition (I think it is not important)
State: Active
Type: Linux
IP: xxx.xxx.xxx.xxx
Model: Linux
Vendor: net-snmp
Contact: Root <root@localhost> (configure /etc/snmp/snmp.local.conf)
Location: Unknown (edit /etc/snmp/snmpd.conf)
OID: 1.3.6.1.4.1.8072.3.2.10
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
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 i686 i386 GNU/Linux