I recently updated my MSI Wind U123’s BIOS for various reasons, and I ran into an problem whose solution I’m offering up in case of issues from out there. Per the instructions from MSI, I flashed the BIOS, powered down, and removed the battery. MSI’s site didn’t specify how long to remove the battery, so I removed it for a 10-count (a slow 10 count).
I put the battery back in, and Windows XP refused to finish booting, instead sitting in the XP startup animation forever. Safe mode booting stopped at Mup.sys. I attempted to boot via CD to use the recovery console, but even that hung up. Frustrated, I made a USB stick with Ubuntu Netbook Remix. That also refused to go far beyond the bootloader.
The solution turned out to be to remove the battery for a good few minutes, then put it back in. Once that was done, all was well again.