As Phylum says you can get an SDD to run your operating system off of, and use a HDD for everything else. Or simply partition your hard drive to keep your system separate from the rest of your data to make OS re-installation easier - Make sure you give Windows 7 50 or 60 GBs of space though, and
you can turn off your page file/hibernation usage to save space if you don't think you'll need them. They'll take up more space depending on how much RAM you have.
Speaking of RAM, 8GB is normally fine for pretty much everything these days IMO unless you do heavy video editing or run RAM demanding apps like Photoshop - You can always save money now if your motherboard has some slots free to add more RAM later, but then it's not like it's very expensive.
Seconded on what Manco said on PSUs.
Also my friend recently upgraded his computer and has that very same case - It's quite decent and has plenty of fans on it already, but make sure you have adequate cooling anyway. It's something I regret not doing when I bought my latest rig 2 years ago...
Lastly you may also want to invest in a second 1 TB HD in a caddy, then regularly backup your hard drive contents using
Allway Sync or another program (Windows backup sucks, don't use it), depending on how much you value your data.