Which would the best upgrade from 8800 GT

HD5770 is a good upgrade from 8800GT, HD5770 is faster but draw less power from PSU...  

What happened to your 8800GT?
What about your monitor? size?

My GPU began to heat up, the idle temp was around 71c, but after i cleaned up the dust, its not at 62C

Also, i am not able to update my drivers to 257.21, i get a BSOD screen at windows xp boot up.

Monitor is Samsung 226BW

The HD5770 would be a good choice as wa1 said. The 8800GT was probably struggling with current games a fair amount at 1680x1050 while the HD5770 should do very well and also give you DX11 compatibility(although you wont be able to use it until you upgrade from XP.)

Then HD5770 is good for your range and setup...  

How old is HD 5770 ? Is it a new card ?

If you want a card for a long term, save more money and get HD5850, you'll good for a long time with that card...  

Yes, it is the latest series by ATI. Nvidia has yet to release any cards for their new series in the price range you are looking at. The closest is the GTX 465 for $250 but for $100(66%) more you'll only gain about 20-25% in performance over the HD5770. For something better that's more reasonable in price/performance you would need to spend $300+ for an HD5850 or GTX 470 but I don't think that is really necessary at your resolution.

just wait a while , the prices of the GTX470 all coming down and since you have a good power supply you can take it . the 5770 is not that strong and the drivers are not that good .

The drivers are fine and the HD5770 is quite good for his resolution. He will be able to max out a large majority of the games out there.

Guys, so should I wait ? Is there any successor planned for 5770 ?

I have been out o f the tech loop for some time.

Are there any new architectures coming out ? Should i wait for the new tech ?

HD5770 is good, no need to wait for a new tech...
It MUCH better than 8800GT...

After seeing the Graphics Card Hierarchy Chart
http://www.tomshardware.com/reviews/gaming-radeon-hd-ge...

8800 GT and 5770 are in the same hierarchy, so i dont think the upgrade from 8800 would be a big one.

But 5850 looks interesting

I think you were looking at the laptop version, the desktop part should be up with a GTX260 or thereabouts. Don't you just love re-badging.  

The HD5770 will be about 50% faster than the 8800GT at your resolution.