I recently did a reinstall of Vista Ultimate x86 on my stepson's computer due to virus damage preventing me from accessing my hard drive. I had to use my Kaspersky Rescue Disk 10, which discovered and deleted the viruses, before I had access to the drive for a reformat and clean install. The computer is a Dell Dimension E-521 with 4GB of dual channel DDR2 RAM. I have in excess of 3GB of RAM available so I know that not having enough memory is not the problem. I allow Windows to manage the page file. Anyway, I now have the problem of not being able to install SP1. I ran an extended memory test using the Windows memory diagnostics I downloaded from Microsoft and memory tests using memtest from memtest.org before I reinstalled. All memory tests passed with flying colors. When I attempt to install SP1 it shows the restore point being made (Preparing to install) and then I get the separate install window for the service pack. It then installs for no more than one second and shows the installation as successful. When I view the update history in Windows Update it shows as being successfully installed but when I use Belarc Advisor, winver or check the System Properties the service pack is not listed. When I go to Control Panel, Programs and Features, Installed Updates there is no listing for SP1, which also verifies that it has not been installed. In addition, whenever I check for updates the Service Pack 1 is listed as an available update. It has installed "successfully" ten times or more, yet it has not installed. I researched the issue and subsequently went to Microsoft's website and downloaded and installed the update that fixes Windows Update problems due to a language pack not installing completely, thinking that maybe the Chinese Simplified language pack only partially installed. Of course, before doing that I checked the update history in Windows Update and the installed updates in Programs and Features, verifying that the language pack had indeed been installed. I logged into my stepson's account and verified that his user account did in fact display Chinese Simplified. It is also visible in my user account when I go to Control Panel, Region and Language, Keyboards and Languages, Choose a display language. I did more research and discovered a hotfix for Windows Update's failure to install problems and downloaded and installed it. Neither one of these fixes solved the problem. It's a never-ending loop. Installed, offer it again, installed, offer it again, on and on and on and on. I then did a System Restore back to the point before I attempted the first SP1 installation. SP1 was again offered to me and the same endless loop presented itself again so I undid the restore. I ran another chkdsk /f /r and no problems were discovered. I did another sfc /scannow and no problems were found. I again ran both memory diagnostic CDs that I had burned from ISOs and all memory tests passed, for the second time. I'm stumped. Does anyone have an answer to my problem? I recall from a few years ago that certain Windows Update files can be renamed or deleted and that doing this sometimes solves a Windows Update installation problem but as I recall it causes Windows Update to delist all the previously installed updates. I'm aware that Microsoft offers a standalone installer for SP1 but it's not to be used for installing the service pack on a single machine so I haven't gone that route. Thank you in advance for your time and any assistance provided. C.B.