upgrading from 4.7 to ecc 6

I want to upgrade from sap r/3 4.7 to ecc6.

Presently I am using a laptop, with 1 GB RAM and 160 GB hard disk. The RAM is upgradable to 2 GB RAM only. Can i use an externl 500GB Hard disk through USB2.0 port and intall ECC6.

The operating system shall reside in my laptop and the applications shall reside in the external hard disk. Can you please tell if the system shall work. Or if work the response time shall be too high to be of any use.

Please advise.

regards