I'll just document the "bugs" with windows 7 64 bit edition running on the HP nx6125 - hopefully it'll save anyone else the bother of installing it only to find it doesn't work acceptably.
- After a hybrid sleep/suspend, the screen brightness is fixed at minimum brightness, and won't adjust using control panel, the hotkeys, or the power adaptor. A reboot or power off then on again solves this. It is also solved by entering hibernate
- After a suspend/hybrid sleep, the screen starts flickering badly after about 30 seconds, showing vertical lines and blocks in the bottom half of the screen. Closing and re-opening the monitor or changing screen modes does not help. Changing display adaptor drivers also does not help. A warm reboot or hibernate again fixes the issue.
- The "mute" light stays on even when the system is powered off. After shutting down the computer, or entering hibernate, if the sound was muted before shutting down the light will stay lit even though the system is powered off. This runs down the battery fully within about a week. Pressing the mute button does not turn off the light, however removing and re-inserting the battery does. Starting the computer to show the bios setup screen also turns off the light.
- After a suspend, the fingerprint reader sometimes no-longer works. I haven't tracked down the cause of this, but it appears to be a software timing bug where the fingerprint reader software tries to access the reader before it's ready.
- Hibernate is unreliable. It works 6 out of 10 times in my trials with no extra programs or services running. The hibernate itself always succeeds, but resume often fails. Sometimes it freezes before the screen mode switch, and if this is the case you will be prompted to try again on the next boot, but retrying always fails in the same way. Sometimes it fails after the screen mode switch after running for a couple of seconds - usually it works fine for about 3 or 4 seconds, just long enough to type the start of your password, before freezing (no mouse movement and caps-lock lights don't change state). If it fails in the 2nd of the two ways, when you restart the computer you will be prompted to send a bluescreen error report (STOP 124).
- No driver that I can find seems to support CPU frequency scaling, so battery life is seriously reduced.
- The s-video out works, but when you disconnect the cable you will get screen corruption. To fix this, press the WIN+P (windows logo key and P) twice, followed by enter. You may need to do this up to 3 times. When you log out or switch user, you may need to do it again. A side effect of this workaround is often you can "loose" the mouse to the right of the screen, because windows thinks the svideo cable is still plugged in. Unfortunately, ATI has given up supporting the ATI x300 chipset on windows 7, so it looks like this issue wont be fixed. A reboot fully clears it.
After all those complaints, there is one positive thing:
It appears that Broadcoms x64 driver for the wireless card works considerably better than their 32 bit one. It stays connected to a wireless network for at least 2 hours before dropping out, and seems to have much greater sensitivity (it shows, and will connect to, networks at much greater range). The bug where a network would show in the networks list but connection attempts would always fail instantly seems to have been resolved. I can't comment on how well it works with the bluetooth because I removed the bluetooth module years back when it disrupted the wireless.
I hope the above will inform anyone planning on installing Windows 7 on this now pretty old laptop. If anyone knows any fixes\workarounds to the above, I would be very grateful!
EDIT: As mentioned in the comments, these nx6125's have a problem where the plastic around the keyboard peels off. The best solution I've found is to just pull it all off, and then use a fingernail to take the shiny grey paint off. That leaves a smooth black surface. If it's a bit sticky, use some nail varnish remover to take the paint remnants off. It looks way nicer like that than with all the bubbling paint. Also, if you're feeling adventurous, use a very thin layer of acrylic paint to change the colour. Use ~3 very thin coats - the paint I was using dried in about 10 minutes, so I got the whole job done in 30 minutes, and it looks way better.