PA Systems :
I gather than from the above suggestions that a 128gb SSD would be plenty of room for Windows and installed programs? I'm not entirely sure how to find out exactly how many GB my installed programs take up. Currently I'm running most of them off another partition on the main drive.
128g is more than enough for windows. As for all programs, that depends on how many programs you have. If you install programs only and have supporting data folders, etc located on a hdd, then yes, you can install a lot of programs. To check your current usage (as an estimate), look in the install folder for each program and see how much space it takes. I have a 120g ssd, but I use it primarily for windows, utilities and often used programs only - games and other space hogs get installed to a separate hdd where boot speed is not critical.
As an aside, please create a new thread when you have additional questions. I understand your posting on this thread, but your question is not directly related to the op's original question. Just a matter of forum etiquette.
Mark