EP43-DS3 + memory slowing problem.

hello,
yestrday i have got a new 2gb memory kingston ddr 2 to my pc so i went to install it.
before it i had 1 gb so after that i installed in on the motherboard i have got total 3gb.
before i installed the new 2gb my system and my pc work perfectly without now problem.
after i have installed the new 2gb my system become very very slow, i'll give few examples...
*for the windows i have to wait like 3-5 min to load up which in normal time took max 1 min.
*winrar works very very slow when i try open a 100 MB it take me like 1 min which normal it took 5 sec... u can guess what happen when i try open a 6 GB files, while it take me now over an hour ! ...
*i also think my CPU is a little bit high, alought its not reach the 100 % but still it hardly stays in 0 % and its always with activity.

I have tried to remove the 2GB and keep staying with the only 1GB but i still had this problem. but problem still remains. i also tried work only with the 2GB , and still got the problems. i have tired to change the slots on the Motherboard but still same problem.

i was thinking i might have some sort of virus but after scanning my pc few times with several AV i refused this option also..
i was trying to set the memorys on another pc to see if they arent the source of problem and they works fine on the other machine.
i was thinking my problem is somwhow related for the Motherboard since i cant find any other problem + and thats why i need some sort of help since im lost ..

i also add a screen of my taskmanger so u'll see my cpu is always in movment
link : http://img241.imageshack.us/img241 [...] geruv5.jpg

my rest machine is :
Intel Dual Core E8400
got 2 memort sticks as i said : kingston 1GB + kingston 2GB both 800MHZ
WestrenDigital 160 GB SATA
MB : EP43-DS3
Radeon H4850 512 MB.

i'll like to thank anyone who can give me some kind of help, thank you...

what do u mean? how can i do it? this may effect that make my pc slow?

hi.. thank you for ur answer .. i have done this trying to set 1.5 and also 1.7
but i still having the same issue.. actully i think even my system works slower now.. but if i try to open rar files of 100 mb against its takes around 50-60 secs...
any other idea??
thank you.

i'll also like to add that games even not a big one like football manager.. it uses a lot of the cpu.. but eventho the cpu is around 60 % i dont hear my pc and my cpu overworking.. if u understand what i mean.

ye.. tired couple of time to scan my system with AV ( norton & adaware )
and i did defrag 2 times... still the same...
i have to say that my pc is like 1-2 month old and my last format was like before 3 weeks.. so my system and windows isnt really full of staff.. it was runnning so perfectly until that slowest problem happened ....
any other ideas?
thank you.