1) You can use Bootcamp which is Apple's solution to switch between both OS's... Hold down option on the Mac chime to pick.

The other solution would be to buy Parellels and run Windows within Mac OS X.

2) They make Bejewled for mac. There are other better java websites out there which don't force you to be on a PC like MSN game zone... I bet your gaming needs could be satisfied with dashboard widgets...