Windows 7: Internet Connection Suddenly Stops When I Download Files

Sorry for my bad english...
Before a week i upgrade my hdd from 300Gb to a newer at 500Gb and i add a 4 GB RAM , now totally i have 6GB Ram
I install Windows 7 Ultimate x64bit
I install all drivers properly but i have a problem , when i download files after some minutes the internet connection stop , windows responds slowly , and when i press the restart button from windows start menu takes much time to logout from logon page

What browser? What version? What programs are in your startup menu? In your system specs you list 2 different types of memory, Samsung & Kingston, is that correct or is there only one brand?

Please post back with the above information.

The problem is not only when i use broswer, for example when i use DvdVideo Soft : Free Studio to download mp3's internet conection stops...
The programs for startup menu are :
Bitdefender 2012
BitTorrent
JDownloader
Mozilla Firefox
Program Folders are :
Bitdefender 2012
Catalyst Control Center
Dell Support Center
DVDVideoSoft
K-Lite Codec Pack
Lineage II
WinRAR
Your Uninstaller! 7

and the defaults windows programs and folders

The Samsung memory is the memory which my laptop have when i buy it and the kingston is the memory which i add when i make the upgrade at my laptop one week ago...The details which i have in my system specs i copy it from Lavalys Everest

The Total Ram Is 6 GB
Samsung M471B5773CHS-CH9 is 2GB and Kingston 99U5428-046.A00LF 4GB

Can Anyone Help Me??

Try the following steps in the order listed;

(Prior to doing any of the following Click "Start" type "System Information" in the caption box and under "System Summary" in the right hand column, what is the number displayed for "Installed Physical Memory" and "Total Physical Memory". Does "Installed Physical Memory" match the number you have installed?)

1. JDownloader could be the cause. I have not fould a need to use any additional software for downloading files with Windows 7, so I would suggest you try uninstalling the software as a starting point and test the results.

2. Bitdefender is not on my list of recommended software. I prefer using Avira, they have a free version which provides most of the benefits of the paid version. You can visit their site at, http://www.avira.com/en/avira-free-antivirus, to download the software and see a side by side comparison of the free and paid version. It is advised to uninstall Bitdefender prior to installing Avira.

3. Your problem may be with the new ram. Many times mismatched ram will not functionally propertly and the system will display performance problems. If you can afford it, I would suggest replacing the ram with matching types.

Please post results.

I doesn't changed by my self the ram, it changed by my technician...When he do the upgrade he just change the HDD and add the 4GB Ram and After i do the format...

After reformatting have you been to Windows update to download all the required updates for your system?

Yes the last updates i do it today

I remove the 2GB ram and i do a test if the internet stop suddenly...

I complete the test and the internet stops again