I just bought an MSI twin frozr Radeon 7950
and I have two monitors.
The card has 1 DVI, 1 HDMI, and 2 mini displayport. How should I connect my monitors? One DVI and one HDMI? Or is it bad to mix signals and I should use the mini displayports? If that is the case, should I use 2 DVI adapters or 2 HDMI adapters?
Anything you wish! It doesn't make a difference as long as your monitor supports it. DVI is usually more accessible (a lot of people have left over DVI cables from the last decade or so of LCD monitors). HDMI and DP monitor cables are more rare since most new monitors don't come bundled with cables like these.
Performance wise, they are the same.
If you are worried about HDCP, then check to see if you have HDCP over DVI (i'm guessing any monitor these days will have that, I never had any problems with this).