Yes, no problem there. 60GB would be tight, but 90GB will be enough if you disable hibernation which will save you the amount of disk space equivalent to how much RAM you have (8GB in this case). A Windows 7 64-bit install should be around 30GB which will leave enough space for a couple of games. A secondary HDD should be used for media storage (you can probably just use whatever you have now).
Also, I went with a P67 chipset motherboard in my selection because you wanted discrete graphics and won't need SSD caching which are the two main advantages to Z68 over P67. Plus it saves some money and that open box buy is a really good deal on that motherboard.