how to open games in Chankast

i recently downloaded Chankast, and a few ROMS which i hav unzipped or unrarred or whatever its called, but, how do you actually OPEN these games in Chankast v.25?

the games are Grandia 2 disc 1, Grandia 2 disc 2, Power Stone 2 and Crazy Taxi 2, my computer is a windows 2000 and i have no idea of anything else about my computer

I have the Bios if that helps any

EDIT: i found a video tutorial on youtube by searching "video tutorial emulator dreamcast" i watched the first one by chaochaochao and followed the instructions. i mounted and unmounted the Grandia 2 disk 1, then opened up chankast, but it just comes up the chankast screen, and when i press run -> start or whatever it comes up:

Chankast_alpha_25 has caused an error in
CHANKAST_ALPHA_25.EXE.
Chankast_alpha_25 will now close.

if you continue to experience problems,
try restarting your computer.

any help would be good thankyou =]