Hi
Download some preinstalled workbench like Amigasys or Amikit. I have amigasys, and it is rock solid!
http://amigasys.fw.hu/Also, do a clean install for WinUAE(use the zip version), pack it to a directory (d:Winuae/) and remember to put in the kickstart rom (3.1).
Now if you still have an unstable system, then I guess it is time to reinstall windoze...
:-D