Windows 7: BSOD ntoskrnl.exe+4b16cc

hello.
i have recently yprade my vga card from 5770 to 6850.
since i made that change,at forst boot nono of my usb work at all!
i delete the upper filter in registry and then usb work!
since then i have bsod with this

i have test memory with memtest and all is ok.
i have unistall ati drivers and install it again,but same again.
make cmos reset,nothing.
sfc /scannow,none problems.chkdsk,none problems.
i have one bsod a day,mostly while i am on internet!
never while playing games!

please help!

A "stop 0x124" is fundamentally different to many other types of bluescreens because it stems from a hardware complaint.

Stop 0x124 minidumps contain very little practical information, and it is therefore necessary to approach the problem as a case of hardware in an unknown state of distress.

Some generic advice.

If you are overclocking STOP.
Return to the default settings at least for now.

If you are running a RAID update its driver.

Prime95 Setup:
- extract the contents of the zip file to a location of your choice
- double click on the executable file
- select "Just stress testing"
- select the "Blend" test. If you've already run MemTest overnight you may want to run the "Small FFTs" test instead.
- "Number of torture test threads to run" should equal the number of CPU's times 2 (if you're using hyperthreading).
The easiest way to figure this out is to go to Task Manager...Performance tab - and see the number of boxes under CPU Usage History
Then run the test for 6 to 24 hours - or until you get errors (whichever comes first).
The Test selection box and the stress.txt file describes what components that the program stresses.

I'd suggest that you first backup your stuff and then make sure you've got access to another computer so you can contact us if problems arise. Then make a System Restore point (so you can restore the system using the Vista/Windows 7 Startup Repair feature).

In Windows 7 you can make a Startup Repair disk by going to Start....All Programs...Maintenance...Create a System Repair Disc - with Windows Vista you'll have to use your installation disk or the "Repair your computer" option at the top of the Safe Mode menu .

Then, here's the procedure:
- Go to Start and type in "verifier" (without the quotes) and press Enter
- Select "Create custom settings (for code developers)" and click "Next"
- Select "Select individual settings from a full list" and click "Next"
- Select everything EXCEPT FOR "Low Resource Simulation" and click "Next"
- Select "Select driver names from a list" and click "Next"
Then select all drivers NOT provided by Microsoft and click "Next"
- Select "Finish" on the next page.

Reboot the system and wait for it to crash to the Blue Screen. Continue to use your system normally, and if you know what causes the crash, do that repeatedly. The objective here is to get the system to crash because Driver Verifier is stressing the drivers out. If it doesn't crash for you, then let it run for at least 36 hours of continuous operation (an estimate on my part).

If you can't get into Windows because it crashes too soon, try it in Safe Mode.
If you can't get into Safe Mode, try using System Restore from your installation DVD to set the system back to the previous restore point that you created.

when i will make this procedure with verifier and have a crash or bsod,do i must make again the same procedure in safe mode?
this procedure of verifier is for one time?is always running after the first time?should i must stop it some time? and how?