First what you need to do is check the discs for scratches, regional coding (PAL/NTSC). Your next step is to perform a System Cache clearance. Refer to the following article: http://support.microsoft.com/kb/971755 If that fails to fix your problem, then remove the hard drive and try play the games then. If none of the above steps work and your console is in warranty, you can get it repaired free of charge. Visit: http://myservice.xbox.com If your console is out of warranty, there is an online charge which differs between regions, in the UK it's £81.60, and around $110 in the US. Any modifications to your console will negate your warranty.