Windows 3.X versions:
While playing, type xyzzy, then press Enter, then Shift. Now minimize all your open windows except for Minesweeper so that you can eaisly see your desktop. A small white pixel will now appear in the upper left corner of the screen when the cursor is over an unmined square and then disappear when the cursor is over a mined square. If you are having trouble seeing the pixel then you might try using a solid, dark color background.
Windows 3.1 AND 95 versions:
Right after starting the game hold down both mouse buttons until the smile face makes his mouth into an O, then press the Escape key to stop the timer. If for some reason you want to restart the timer, just minimize the game and bring it back up again.
NOTE: The first square clicked is NEVER a mine.
Also, here is something for those of you wanting to impress your friends. Run notepad and oped the file winmine.ini in the Windows directory. You can change the best times and the names of the people who got them..
Special thanks to Simon Hume and Matt Andrews for their contributions to this section. Thanks Simon and Matt!