Windows 7 upgrade laptop


I currently run windows 7 home on my laptop , its an oldish laptop but works perfectly fine still looks brand new but the memory is poor 2gb ram and 80g hdd i wanna upgrade the HDD too a SSD too make it run faster but how would i know what SSD i would need?

the laptops only used for basic browsing and TK and e2 requirments but i wanna keep images on my laptop aswell but the hdd is poor.

the laptop is a samsung model NP-Q45

any helps appreciated from the techy guys.