Acer laptop issue, please help

All right here is my problem. I bought a Acer laptop (5100 series) from a retailer with 5 years warranty and within the first 6 months it came out with a memory leak, and the warranty replaced it with a new motherboard, which eventually changed the Vga from 128 MB radeon to a 512mb radeon because its onboard. Now i get a small resolution issue that when i install new drivers every things normal until i restart. After restart the resolution is like 800x800 even though it is actually set to 1280x768. Check out the two images, one is before restart and other is after, Help would be really appreciated...

After restart - http://images.trademe.co.nz/photoserver/35/50356035_ful...
Before restart - http://images.trademe.co.nz/photoserver/54/50356154_ful...

If you see closely you can see the difference in desktop shortcuts, and the task bar icons. The resolution is 1280x768 in both cases.

thanks