Memory usage stays at 100%

Hey everyone,

I know a few people that are having this exact same problem.

I am running Vista x64 Ultimate with 4gb of RAM.

When I put in a CD and install a program, my Mem usage sometimes goes to 100%, and stays at 100% even when it is finished installing. Everything runs insanely slow, and I usually end up holding the power button to restart (if I click on the start menu to restart, it takes 15-20s for the menu to come up).

I say it happens sometimes, because it doesn't always happen. It is hit or miss. It sometimes also happens when doing other tasks (see below).

However, when I open up task manager (and display all processes), I do not see any processes that are using an insane amount of memory. Everything looks normal.

Also, today I was backing up ~3.5gb of files from my hard drive to my external drive. My memory usage went to 100% and stayed there, just like I mentioned before (had to power off).

Just to get all of the starter questions out of the way:
-This is a fresh install of Vista x64 with SP1 (SP1 is up-to-date)
-I do not have any viruses
-I do not have any spyware
-I have ran memtest for 16 hours just to make sure it wasn't my RAM
-I have no messed with the pagefile
-UAC is enabled

Also, when I run a program like prime95, my memory usage goes to 100%, but when I hit "stop", the mem usage goes back to 30-40% like it should. So things are working okay.

I have had this system up since June. It is not a HUGE issue, because most of the time I am not installing anything, but when I do install something, it sometimes requires me to reboot.

Any help would be greatly appreciated. Again, it is not an extremely serious issue, but this is annoying as hell haha.

EDIT: I also understand the whole Vista pre-fetching thing (I study computer science) so I know the difference between pre-fetching and the bug I mentioned

I can't help but just wondered what anti-virus program do you use, I believe that some versions of NOD32 have had problems with high CPU usage when scanning large files.

As I said I can't help you this was just a thought on my part

I am using Avast! as my antivirus program.

I had the same problem but only when running Windows mail. The system would lock up and I woulds have to shut dow the program and restart and it would correct itself.

I had a problem just like this a bit ago before my current problem and i found that it traced back to my sidebar. My side bar was using 90+%of my memory. I would go into the task manager and end the side bar process and it would fix the problem and then just ask to restart the side bar. It is up to you if you want to run the sidebar I like it, but it is a resource hog if you have a lot of stuff running on it.