You can specify the ESXi versions for the downloads by editing this configuration file before the first synchronizsation:
C:\Program Files (x86)\VMware\Infrastructure\Update Manager\vci-integrity.xml
There's a part that looks like this:
<contentSettings>
<hostInclude id="0001">esx-4.0.0-INTL</hostInclude>
<hostInclude id="0002">embeddedEsx-4.0.0-INTL</hostInclude>
<hostInclude id="0003">esx-4.1.0-INTL</hostInclude>
<hostInclude id="0004">embeddedEsx-4.1.0-INTL</hostInclude>
<hostInclude id="0005">embeddedEsx-5.0.0-INTL</hostInclude>
<hostInclude id="0006">embeddedEsx-5.1.0-INTL</hostInclude>
<hostUpdateEnabled>true</hostUpdateEnabled>
<vaUpgradeEnabled>true</vaUpgradeEnabled>
</contentSettings>
I've changed it to that:
<contentSettings>
<hostInclude id="0001">embeddedEsx-5.0.0-INTL</hostInclude>
<hostInclude id="0002">embeddedEsx-5.1.0-INTL</hostInclude>
<hostUpdateEnabled>true</hostUpdateEnabled>
<vaUpgradeEnabled>true</vaUpgradeEnabled>
</contentSettings>
I already think of reinstalling the Update-Manager to get rid of ESX(i) 4.x Updates, that I dont need, since we're using 5.1. Maybe this will fix the HP Update issue, too. If not, I've at least got a cleaner repository =)