My advice..........Don't create extended partition, and dump linux there.
Remove/delete that extended partition and you'll have extra free partition(30G).
From that free space, create partition for linux swap and Linux partition(ext3).

The xp keep restarting has nothing to do with linux.............probably a bad installation or problem with hardware.
Check for any losen card in your pc. I had this problem before.....and found out my networkcard not properly inserted.