My System:
AMD Athlon 2 x2 250 3ghz
4mb Ram
XFX Radeon 4550 1gb
Realtek Sound card
Windows 7 Home Premium
I downloaded RC3 today. Unfortunately I still have the issue of the display dropping down into a small box on the bottom left of the screen. But as was the fix for RC1 and 2 putting the /sim/ati-viewport-hack=1 into the properties works. Just FYI that I have tried only 4 aircraft. C172, B1900, Piper Cub, B105. But I had the issue with all 3 until inputting the view-port property.
My sound still stutters/skips as it did in RC1 and RC2 on all of the above aircraft except the B1900. I am not sure why it works fine with that one.
Hope this helps someone.