XP SP2 Access Denied

I can't update to SP2. Here's part of the log where the error occurs:
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483.984: Copied file: C:\WINDOWS\System32\spool\DRIVERS\W32X86\3\hpfud50.dll
492.000: PruneCatalogsFromHotfixes:RegQueryValueEx Failed: 0x2
494.094: Num Ticks for Copying files : 264656
494.109: DoRegistryUpdates:SetupInstallFromInfSection Failed for ProductInstall.GlobalRegistryChanges.Install error: 0x5
494.109: INF_REGISTRY Failed
494.109: DoInstallationoRegistryUpdates failed
503.234: Unregistration of sprecovr successful
503.234: Access is denied.
13890.156: Message displayed to the user: Access is denied.
13890.156: User Input: OK
13890.156: Service Pack 2 installation did not complete.

Select 'OK' to undo the changes that have been made.
13891.484: Message displayed to the user: Service Pack 2 installation did not complete.

Select 'OK' to undo the changes that have been made.
13891.484: User Input: OK
13891.500: Starting process: C:\WINDOWS\$NtServicePackUninstall$\spuninst\spuninst.exe /~ -u -z
14148.453: Software Update Rollback has completed with return code 0xbc2. This rollback requires a reboot.
14148.453: Service Pack 2 installation did not complete.

Windows XP has been partially updated and may not work properly.
14158.484: Message displayed to the user: Service Pack 2 installation did not complete.

Windows XP has been partially updated and may not work properly.
14158.484: User Input: OK
14158.484: Update.exe extended error code = 0x5
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I'm under the general impression that I don't have permissions for some registries...but which ones...and what do I do?

-Brett