I say again, the PRACTICAL net effect of explorer.exe restarting, the system restarting and or crashing is the same. You must either wait or have the knowledge to manually restart the shell. NONE of which helps the OP with their problem.
This is the AT OS forum, typically if information is posted that is not technically correct members will point out the correct information to clarify. This is usually a good thing because it helps keep us on our toes and makes us think twice before posting.
The likely root of OP?s issue was pointed out in the first response, which was made by me. If you want to argue the worth of posts on this thread than I shouldn?t be your target.
If the shell process is killed it will automatically restart itself, the duration for this to occur is typically less than 10 seconds. When the shell is killed on a system that is running properly it will not ?crash your machine?. This is an important clarification to make because by telling them that it will cause the machine to crash you lead them to believe that they cause more damage by doing so, this is simply not true.
The net result and information for the OP is the same.
1. The machine is likely infected
2. The OP would not have caused serious damage were he able to kill the explorer.exe process like originally attempted; in fact I would not consider it an unreasonable thing to try.
The reason I say it wouldn?t be an unreasonable thing to try is if it were the explorer.exe process that was spawned under the user context of their account when they logged in and some legitimate shell plug-in ran away (i.e. something that renders special icons, etc.) it would have cleared out that memory and then explorer would have restarted with a much more reasonable load.
Also FYI if he able to see process information than he?s probably logged in as an administrator; however if he is unable to stop it than the process is probably running under local system security context (which the ?real? explorer.exe shouldn?t be doing). Odds are good that the explorer.exe he saw on the list is something else masquerading as the shell.
His failed attempt to stop explorer.exe (with the access denied error) is simply another likely indicator that the machine has been infected.
Obviously I?ve made some assumptions here, my first post was not designed as the end-all-be-all solution; merely a suggestion of a path to follow.
BTW - Windows has only been around a little over 20 years and AFAIK the explorer.exe shell didn?t get created until about 12 ago.