problems HD install on Dell Inspiron 8100

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I have installed Knoppix 3.4 with 2.6 kernel, which unlike 2.4, detects my network card. The screen is UXGA (1600x1200) and uses an ATI Radeon 7500 64meg video card. The HD install does not properly detect the video card and defaults to a "basic" card plus a screen with no more than XGA resolution. I have tried changing the XFree86-4 file to include 1600x1200 as default but with disastrous results as it causes the installation to not reboot properly , requiring a complete re-install. Can anyone help?
ps Unlike previous versions of Knoppix the installation does not shutdown properly - ever. Other than that and problem with screen and video detection it is really good.

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I found the answer from an earlier post on this forum: I booted from cd forcing a UXGA mode and then replaced the current XF86Config and XF86Config-4 files in /user/X11 by the cd-created ones in the ram disk. No solution to shutdown probelm yet, though. I will keep experimenting and looking.