HelP!! Why won't my Dreamcast play a lot of games?

[Megalexxx]

I can see 2 possible reasons :
1) your DC is "too" new, and can't play Audio/Data copies. In that case, you'll have to make them selfboot using Bin2Boot
2) your DC or your TV is PAL and doesn't support your NTSC games. Try to find some patches (on DC Copy World), or try PAL Patcher.