Found a manual for that MB at:
[link|http://wwwbzs.tu-graz.ac.at/edv/prodinfo/asus/p55tp4n.pdf|http://wwwbzs.tu-gra.../asus/p55tp4n.pdf]

From it:
Multi-Speed support: Supports one 75-166MHz Pentium CPU on a ZIF Socket 7.


And no, don't happen to have a 166 laying around.

Edit: Asus' website lists 2 BIOS updates for that MB:

[link|http://www.asus.com/support/download/item.aspx?ModelName=P/I-P55TP4|http://www.asus.com/...elName=P/I-P55TP4]

You might consider applying them, could be Y2K mods.