Windows Error: "System could not allocate the required space in a Registry log"

I recently had this issue on my dad's Acer laptop with Windows XP: "System could not allocate the required space in a Registry log". After googling, I found the fix: "Delete unneeded files from the system partition and then retry the operation." But, there's was an issue: I get the error even before getting on to the login screen. So, I couldn't delete any files and free up any space to get the computer started. 

The next fix I thought was to try the safe mode to get into the computer, so that I could delete some files. Unfortunately, it didn't work either as I got the same error before getting into the files system.

Finally, I removed the hard drive, put it on to an external hard drive enclosure, and plugged into another computer. Then deleted about 500 MB of files and plugged it back into the Acer. The computer started fine without any errors.

Hope this would help someone.