Hi,
I set up my RH8 with a 4MB VRAM while setup. My RAM is 512 and builtin AGP. Now I can't use Xwindow. But i need to use that. So I need to increase my VRAM. From where I can change the Value?? where is the conf file?

So your built-in VC has 4MB Ram. Does your sytem share system Ram with video card too? If not you should still get X desktop going. Review how RH8 sets up XF86 or xorg. In Section "Device" Driver try correct VC driver or vesa or vga driver in XF86Config-4(or xorgconfig)and under that Driver put in Videoram amt in kb(4MB=?kb). Then in Section "screen" default depth try setting of 16 if 24 doesn't work. You may be limited to 800by600 desktop size too.
If adjusting x settings doesn't work then maybe a new video card with more ram is indicated. You should not have though. Hope this helps.

I have tried it... no result... VRAM shares RAM... i set for 256MB=blabla kb but nothing. I even used redhat-xconfig but result = 0... now all i can do is to install it newly... not even upgrade... damn!!

From review of other installs it would be better to use 16mb then 32mb(in kb) because if you use more you will get warnings about memory and crashes. Even if you had 512mb ram to share with video card 16 or 32mb/64mb max would be best,even if agp aperture, or similar, was 128mb. Best wishes.