Windows 7: Computer slow, RAM full, no processes using it...

Today, when I powered up my computer, i have noticed that it has been on 'Welcome' for 10-15 seconds, which is more than usual 'up to 1'.
But I ignored it. However, while I was playing game, it froze for a moment several times.
Ignored it again. But, when I started Firefox, and waited and waited and waited... and waited, I have came to a conclusion that my computer runs slower than usual.
I've ran task manager and saw that my RAM memory is 3,98/4 GB full. Also my hard drive is 100% busy all the time. Indicator is constantly on...
Then I checked running processes to find out that they combined wouldn't spend more than 2 GB of memory.
I've already had this problem on my laptop before, but there was some kind of WMP updater or something taking this, but nothing here.
Anyway, I've restarted it and all, and scanned my system and did everything I could think of, but something's wrong.
What is taking my RAM? How to bring it back to normal?
P.S. I have Windows 7 and 8 developer preview installed, but I had it before the problem occured. Win8 is not having difficulties...



Please help...

You came to the conclusion that your PC runs slower than usual? Really?



Sorry, just poking a little fun at ya.

But seriously - what would help us here is if you could provide a screenshot of your maximized Task Manager window, specificially the Processes tab. Please make sure to check the box "Show processes from all users" at the bottom before taking the screenshot.

Let's see what's going on here. Since you observe the slowdown at startup even before your desktop appears, it sounds like a service or background task running under system credentials, rather than a user-owned process.

Make a screenshot of ProcesExplorer: Process Explorer

Well, I've been searching the youtube and the web for something to help me at least a little bit while waiting for answer and I've managed to find a software that brought my RAM to normal:
AMS Network
However, my hard drive is still 100% busy, making my computer still slow.
I'd be grateful if you helped me about it.
If you still need screenshots, let me know...
Tnx.

Well... take a look in here:
(i'm sorry for the dutch language but I think you know where to navigate ?!

Here it is:

What now?

I don't see anything that you can remove but I would try this:
(Disable everything (not microsoft services !!!!)
(So we can see if the HDD is calmer then )

what exactly do i need to do?

Sorry (reload page)

all right!

problem solved.

many thanks

edit:
happened again!

that software for ram was helping until the computer was restarted...