I have recently been forced to reinstall Windows XP. Since then, every time I install Service Pack 3, my task bar does not load when I log in. The only way I have been able to get it back is to repair the install using the Windows XP install disk. This does not help much, however, as I am then left without installed updates. I have tried stopping and restarting explorer.exe and I have copied the explorer.exe from my old install (my computer recognizes the drive but refuses to boot from it now). Neither of those have worked. It would be greatly appreciated if someone could either tell me how to fix it directly or avoid the problem the next time I have to install XP SP3. I am currently on that machine. I'm using the Task Manager to open up the command line.
EDIT: I just thought about it and realized that there's more to the problem. My desktop icons haven't been loading either and nothing in the startup folder runs. I don't know why, but it just occurred to me that this may also be part of the problem. Until now I thought that it was all linked to the taskbar not loading, but now I think there's a bigger problem here.
Update: I'm going to attempt a system restore from the command line to roll back SP3. If that doesn't work then I'm going to repair the install again. The taskbar tool recommended in one of the comments did not work. Neither did running explorer.exe. Some of the answers have not provided enough detail as to how to fix it, such as making a change to an executable file. Others seem to be addressing a different problem altogether. Keep the answers coming and remember that I don't have any kind of graphical explorer interface.
Update 2: System restore did not work so I had to go through the repair process again.