Check ICAProductMinorVersion registry setting
When installing Service Pack 1/Feature Release 1 for MetaFrame XP 1.0 for Windows, you may receive the following message:
"You have a pre-release version of Feature Release 1 for MetaFrame XP installed. Installation over a pre-release version is not supported. Setup will now exit."
• Run regedt32.exe and locate the following key: HKEY_LOCAL_MACHINESYSETMCurrentControlSetControlCitrix: ICAProductMinorVersion
• The ICAProductMinorVersion will most likely be set to "Service Pack 1."
• Delete the ICAProductMinorVersion key and try installing SP1/FR1 again.