also y upgrade to a 240 gb ssd
Because even older games chew up space at a surprising rate. You are going to want to set up your SSD to only contain Windows and your programs and use your HDD for data and user profile storage. Here's a rough space breakdown of what you should expect to get used for some some standard applications:
64-bit Windows 7 = 20 GB
MS Office 2010 = 10 GB
Basic applications (Adobe Reader, Forefox, Chrome, Java etc.) = 5-10 GB depending on what you install
Many current games use at least 5 GB of space but can easily use over 10 GB as well. So you could calculate roughly 7.5 GB for each game if you wanted to install to be somewhat safe.
Here's an example of some games I have experience with:
League of Legends = 5+ GB
Borderlands = 12+ GB depending on DLC
Bordlerlands 2 = 6 GB with no DLC
CS 1.6 = 1 GB
CS:S = 5 GB
CS:GO = 6 GB
DoD:S = 4.5 GB
Civ V = 5 GB
Knights of the Old Republic and Knights of the Old Republic 2 = 8 GB
Torchlight = 1 GB
Torchlight 2 = 1.5 GB
All told that comes to 55 GB of space for games. Add in the ~40 GB for Windows and standard programs and you are over 90 GB. Throw on something like Photoshop or Adobe Creative Suite and you will see a lot more space disappear as well. You only get the fast load times if a program is installed on the SSD, and you don't want to fill it to the brim (never a good idea on any storage device). That's why I recommend a 240 GB drive. The price per GB ratio is still good (often better) at that level as well.
A lot of those games are older as well, so if you plan on playing newer games I could see them easily totally more than those.