Hello Friends

I am having Toshiba Satellite L555D
Its configuration is
AMD turion II Dual core processor M500
3 GB DDR2 RAM
AMD M860G with ATI Mobility Radeon 4100
250 GB harddisk
17.3 inch

I want to install Snow Leopard on an external Harddisk , not on harddisk of laptop .... and boot through USB ...


Which distro will be best ???



Thanks