I am working on a friends computer, it started off with a massive spyware / virus infection that I cleaned using Spybot, Hijack This, Ewido Micro Scanner, Super Anti-spyware and a few virus scanners. The current problem is when the computer starts up and you select the user, explorer.exe does not appear to load. I can use Task Manager to start it manually and everything "appears" to be fine. Upon reboot still no explorer.exe I have checked Google and followed all the instructions I was able to find, but I am still having this problem. (Shell is set properly in registry) To help me solve this, I attempting to install SP3 to see if this helps anything and I am getting to the point of setup that says: "Performing Inventory" and then I get an error message of: ntoskrnl.exe is in use by another application. At this point I suspected a Rootkit, so I went and ran Rootkit Unhooker and found my suspicions were correct. I am fairly sure I have cleaned up the rootkit, as I no longer see hooks in RKUH. I am now installing SP3 without any troubles. I posted the information above to help out other people who get the error "ntoskrnl.exe is in use" as I searched for help on this and was not able to find anything. I will post a follow-up if SP3 fixes my troubles.