It will take over your file. I recommend right-clicking the system tray
Icon for Microsoft Antispyware, and choosing Shutdown.
Then delete the file.
If you have a text editor that will handle the file, it'd be nice to see a
snippet of the content--one way to do this might be to re-start Microsoft
Antispyware and observe the file for a bit of time--and catch it earlier in
the growth period.
I had one Windows 2000 machine on which a similar issue happened. I
uninstalled Microsoft Antispyware, and then later reinstalled it. The
errors.log file has been normal in size since then--still under 1000
characters after several days.
So--take action--it'll crash your machine. If you can, try to get us a
snippet of any repeating error sequence--post to this thread. And
probably--uninstall the beta, and either reinstall and watch carefully, or
wait for the next version and re-test.