WARNING: Switch the power switch on the back of your power supply OFF before working with AGP Video Cards, RAM, or the CPU in any system! If the PSU has no AC switch, unplug the PSU! The RAM, video card, and CPU are connected to +5V-STBY and will be damaged if tampered with while +5V-STBY is active.
Win98SE and later support dual video cards/displays. You mount the video cards and install the AGP card as your primary, then use Display Properties and the extra tab you get when you activate multiple display to arrange your screens. You can use the second display for simple text-only, append its display to your primary monitor, display part of the primary monitor on the secondary, or use each monitor for independent display...
Don't block the AGP card GPU fan with the secondary card, and consider that the AGP card often shares its IRQ with that nearest PCI slot...