unable to install SQL Server 2005 Express Edition SP2

Hi,
Thanks you for taking the time to read this post.

I can't install SQL Server 2005 Express Edition SP2 using either wsus or
Windows Update.

I have tried it following a reboot and with AV disabled. The machine
concerned is a HP ML350 Server running Windows Small Biz Server 2003

I get the following in the logs

Thanks again for your help.

Regards

Gordon

Time: 03/05/2008 12:10:55.135
KB Number: KB921896
Machine: CSAISERVER01
OS Version: Microsoft Windows Server 2003 family, Service Pack 2 (Build 3790)
Package Language: 1033 (ENU)
Package Platform: x86
Package SP Level: 2
Package Version: 3042
Command-line parameters specified:
/quiet
/allinstances
Cluster Installation: No

************************************************** ********************************
Prerequisites Check & Status
SQLSupport: Passed

************************************************** ********************************
Products Detected Language Level Patch Level
Platform Edition
Express Database Services (ACT7) ENU SP1 2005.090.2170.00
x86 EXPRESS

************************************************** ********************************
Products Disqualified & Reason
Product Reason

************************************************** ********************************
Processes Locking Files
Process Name Feature Type User Name
PID

************************************************** ********************************
Product Installation Status
Product : Express Database Services (ACT7)
Product Version (Previous): 2170
Product Version (Final) :
Status : Failure
Log File : C:\Program Files\Microsoft SQL Server\90\Setup
Bootstrap\LOG\Hotfix\SQL9Express_Hotfix_KB921896_S QLEXPR.EXE
SQL Express Features : SQL_Data_Files,SQL_Engine,SQL_SharedTools
Error Number : 28092
Error Description : Unable to install Windows Installer MSI file
----------------------------------------------------------------------------------

************************************************** ********************************
Summary
One or more products failed to install, see above for details
Exit Code Returned: 28092