Is it possible to get convert a hard drive (500 gb ) from a hp G7 laptop into a external HD.

If you can find an external drive case to fit 2.5" drives.

One source for 2.5" external enclosures is IcyDock (http://www.icydock.com). A 3.5" enclosure with a 2.5" adapter like Newer Technologies' AdaptaDrive (http://www.newertech.com/products/adaptadrive.php) could also be used for SATA drives.

Is it possible to get convert a hard drive (500 gb ) from a hp G7 laptop into a external HD.

Yes. Just buy a matching external enclosure. They also make an external enclosure that accepts HDD's that are IDE (PATA) and SATA, for a 2.5 inch laptop sized hard drive,

One such example,

http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=7041055&CatId=2783

,and for a desktop 3.5 inch sized hard drive,

http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=1945393&CatId=2780