Welcome to techIMO*
You mean there are no display on your monitor? The hard drive (HDD) is okay. How's your RAM (memory card)? If there's a problem with the RAM, the display won't show up.
You can have your RAM check and try clean the copper grill (the connector) with a cloth or a rubber. Just rub that part to clean possible dirt that stuck there. And then place it back again on the slot. If the problem still occur, then change a new RAM. 128 MB RAM will be fine for a Pentium 166.
When your RAM is fine, there should be a display and you can even enter BIOS for setup. Good luck. All little help we can do