So judging from what I've read so far, it looks like this combination could run most games up until around 2003ish. Comfortably that is. Just wish my slot 1 440BX chipset board supported 133mhz FSB as this would add a bit of speed overall. Basically trying to get the most out of this chipset as I prefer it when it comes to retro builds. I would've went with a socket 370 board if I could've managed to find one with an intel chipset and AGP/ISA slots.
Regarding the OS, definitely sticking with windows 98 se (normally always do). Besides windows 7, it's my favourite OS due to real mode dos whilst having great compatibility and decent usb support.
Btw, I think what I'm concerned about is that I also have a P4 3.4/6800GT combination on an asus p4p800se board and on max settings C&C2 and RA2 lagged. These games were made around 2002-2003. If my pentium 4 can't handle those games, how could the above combination handle for instance UT2003 or Doom 3? Unless Westwood just badly coded their games...