as long as your PIC video card has real win98 drivers or whatever OS you're using, you can.
remember that the secondary monitor is nothing more than an extension of your desktop... don't expect to play games on it. the good thing about w2k is that it allows you to change which is the primary monitor, so there you can actually play games on any adapter you want.
the most basic way to have dual mon is to get a card with 2 outputs ;-)
the second is just to install another display adapter while using an OS that supports multiple displays. you may have to troubleshoot to get things working due to some driver conflicts...
here are examples of some of the problems i have had:
I. Matrox Mystique (170, the original)... the drivers that came with win98se did not allow me to use the card as a secondary card... i had to use the latest drivers at that time from matrox which worked like a charm =) though the features of "powerdesk" did not work since the card was secondary...
II. creative labs banshee (3dfx chip, should apply to many banshee cards)... the drivers install also installed 3d tweaking utilities and junk which conflicted with my primary video card which rendered both cards caput... my solution, remove drivers for both cards via safe mode... install the primary card, reboot, install the secondary card (the banshee), before rebooting UNINSTALL the 3d tweaking utilities, reboot... worked like a charm.. =)
my primary cards have been a rage fury, and now an aiw radeon... my current secondary card is the matrox card mentioned above...
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microsoft has a list of chips\cards that they have "approved" as secondary cards, of course the banshee is not on the list ;-)...
anyway, those OLD ATI (rage pro, and older) pci cards work great from reading various experiences (not just killbat's)... those cheaper cirrus logic ones do well too...