First, configure your DOS games for IRQ/DMA settings of your sound card - look into Windows 2000 Hardware Profile for this. If that makes them work, good.
Next, identify your sound card and check out the manufacturer's website for drivers that are designed to make those "stubborn" games work under various OS (including Windows 2000). Infact, Creative's website includes quite much material over this.
Still, if it doesn't work (given in step 2 you DID find something), then see if that particular game figures in Windows 2000 Incompatibility list.
Lastly, contact the author of that game/software and ask for steps/fix to make it work under Win2k.