To Tesla_rage and those experiencing blackouts (regardless of brands), please check:

1. PSU not enough power (unlikely if you use true power 500W and above - depending on other items in your rig too).

2. Pirated Windows XP Pro. Very few thought of this: http://thestar.com.my/news/story.asp?file=...1600&sec=nation

3. Unstable driver. Try using CCC 8.7 first. Play some games, don't use those benchmarking apps like Furmark. If games ok, then keep 8.7
Make sure your folder & registry is clean from previous drivers. Use http://www.ccleaner.com/
We are studying your problem now. Give us some time to get back to you. Do you see any artifacts/funny characters on your screen?
Please relax bro. No need to post same thing so many things. We sold hundreds of 4850 GS and we know there are many users with 4GB. It should work fine. We are taking note of cases like XChoit but it's not easy to determine if a problem is Apps/OS/Driver or Hardware-related.

Just feel safe to use 4GB with 4850 GS like many others.

Thank you everyone for the feedbacks, and thanks to those who try to help others. 

We will finalise our reward program for the helpful people here soon. 

Hehe will consider it Btw any idea why my psu make some sound when i stress test my 4850GS, like using ATI tools to scan artifact then theres some high pitched sound coming from my psu lol. When i stopped it, it seems normal my specs is in my siggy

Well, I cant believe Netraid offer such a good service. It is hard to find such a good distro nowadays. What else brand they carry. Next time buy from them again.