High unexplained RAM usage

I have already formatted PC several times but there was no improvement in speed. I have been getting this weird problem with Windows 7, and I apologize if this has been posted and solved before, but I couldn't find anything. So, I don't remember when this started, but my RAM usage is upwards to 80% with 2 GB of RAM. And I am currently running a lot of programs, true, but closing them all does nothing. It's as if Windows is failing to eliminate the resources used by the programs even after closing. The RAM is around 50% on start-up (which seems insanely high...) And it won't go way all that much even if I end every process I can. Anybody have any clues to fixing this? It never happened before when I was using win 7 on the same machine.

System Config:
Processor- Intel (R) Core(TM) i3 CPU M 380 @2.53GHz
RAM- 2GB (Usable 1.74GB)
System Type - 64 Bit Operating System

Thanks

A screenshot of Task Manager - Performance tab when the problem occurs would be useful.

50% memory usage at bootup on a 2 GB system is not insanely high. It is about typical. Memory usage in any modern OS is highly dynamic. The memory usage of processes is by no means a constant value but varies according to the amount of memory available, what the process is doing now, what other processes are doing, and more. Process memory usage at bootup will be trimmed back if more is needed for other applications. I have seen this happen many times.

2GB isn't much RAM for x64 Ultimate, especially if running several programs. I doubt that the laptop was sold with that setup. I suggest either get more RAM or install x86.

Problem have not solved yet.
I am using Acer Aspire 5745 laptop. Today i saw task manager and see that the my browser Google chrome is taking more process so i have uninstalled it.. snapshot attached below:
But after all i feel that my system is yet too slow. Now i am using only Firfox but nothing can happen in speed of laptop.
Before i have scan my system to avast, kaspersky and malwarebyte.
Kindly help me.
Thanks

Sorry, but that screenshot isn't what I asked for. I asked for the "Performance tab".

But it does seem you are asking too much from a 2 GB system running a 64 bit OS. Running both Firefox and chrome at the same time. 2 GB RAM is the minimum supported on a 64 bit OS. Note that the Task Manager is not showing any of the system processes. "Show processes from all users" is needed to do that. Also the "Memory (Private Working Set)" column does not show full memory usage of a process. Having multiple AV products running can have unpredictable results, except they are likely to be unpleasant.