dont use the sblive...just get a cheap isa or pci soundblaster. Mame will be faster in dos on a 733mhz machine. I use a 900mhz p3 machine for my vertical classics cab and its weak....it doesnt play but 90% of the vertical games and Im running dos with an arcadevga card...would not even consider 98 on that machine.
But to each his own.
The geforce 3 wont help you much at all in mame....not win98 or dos....its the 2d mame uses....also your dont need dos drivers for a geforce...however the live would need dos drivers hence the recommendation to get another cheap card if you do decide to go with dos.
however windows 98 is easier to setup. If I recall the minimum requirement for XP is 700mhz. Basing off my experience with my P4 3.6 that barely runs XP well (haha)...that 700mhz would be unbearable.
not to start a big debate here, but there's some bad info in here.
if you can't run vertical classics on your 900mhz P3 its because you are using too new a version of MAME, or you are doing something entirely wrong. I've had XP and MAME .55 running on a 900mhz Athlon for over a year now and it works like a champ.
Also, tha 733mhz would be a good candidate for a stripped down install of XP if you can get some more ram into it. 128mb won't do it IMHO, not even with a stripped install. If you jumped to 256, or hopefully 512, you'd be fine. I've run stripped XP installs on ~600mhz machines and they work fine.
And I know the "cant run XP on my 3.6ghz is a joke, but just the fact that you make the joke tells me you're setup has some flaws or you just dislike Windows. XP is a very good OS, and despite people's usually blind views toward the fact, it scales fairly well with some tweaking.
Just throwing out my .02 here so as not to make MartyNg think he's stuck with DOS only as a choice. You can run XP on a system like that if you wanted, as long as you do some tweaking to the install. 98SE is also a good choice, and i'd personally go that route before I went the DOS route.
DOS MAME installs are not necessary for any computers over 500mhz IMHO.