Startup Registry File Recovery Error Msg

Three months ago I started getting this error message each time I turned the computer on: “One of the files containing the system’s Registry data had to be recovered by use of a log or alternate copy. The recovery was successful.” I hit OK and everything seemed normal. Then the day arrived when I turned the computer on and it wouldn’t boot. The error message said WINDOWS/SYSTEM32/CONFIG/SYSTEM file is missing or corrupt. I had to clean re-install Windows. Everything was fine for about 10 days after the re-install but now the original error message is back: i.e. “One of the files containing the system’s Registry data had to be recovered by use of a log or alternate copy. The recovery was successful.” What is the cause of this error and how can I fix this before my system crashes again?

Jane

System is Win XP Service Pk 2