I have been asked to help with an Acer laptop. It has worked fine with a dual-boot configuration (Arch Linux/Windows XP) for some time. Then the user decided to replace XP with Windows 7, which still worked fine. Weeks later when booting up windows 7 the laptop's PS/2 mouse and keyboard did not respond.
A solution seemed to be to format the Windows partition again and reinstall XP, but the mouse and keyboard didn't respond in XP either. We tried Windows 2000, but without any success.
The only way to get input to work in Windows was to launch it in safe mode or with external keyboard and mouse plugged in before booting (Windows wouldn't recognise them at runtime and the mentioned workarounds worked 1 out of 3 times at best).
In safe mode, Windows did not provide any debug information or error messages related to the problem. I have to mention that the keyboard works fine in the BIOS and both keyboard and mouse (built-in and external) worked fine the whole time from the Arch Linux OS. Any advice would be appreciated.
The BIOS configuration in this laptop is very limited, I doubt that it's causing the problem.
Why would stock Windows XP (the same version that worked before) install different drivers for exactly the same hardware? (yes, there where no hardware changes at all)
I got the install done by connecting external mouse and keyboard (USB) before booting the system: it was the only way to do it.
I'm beginning to think that Windows somehow preserves some configuration from previous installs on another NTFS partition I didn't install it to. This would explain why Windows 7 could mess up my clean XP and 2000 installations: unfortunately formatting those partitions is not an option at this point.
As I mentioned in the original post:
"The only way to get input to work in Windows was to launch it in safe mode..."
This means it works fine in safe mode! And it works in Linux and the BIOS too... So please quit posting "it's obviously a hardware failure" type of answers.