Need Help Picking an External Hardrives

From Us, 2 posts

I have a laptop thats about a year old with a core 2 duo and 1 GB DDR2 dual chanel memory
unfortunatly i only have an 80GB harddrive

I do some photo editing but have about 20GB of just music and more on the way which iss all leagal

i need a external harddrive that i can use to back up my whole computer and store music, photos, vid...on

i had a few questions
first can i run sertain progans off gust the external harddrive
for example could i put photo shop on an external hardrive insted of my own and still use it when i have it hooked up

the other question is what brand shoud i get and what size
i ddont need anything like a TB
but want anought room to store all i want

price range would ke to be under 200
and i want this to be reliable so i dont lose the data i store