FYI I just installed Win 7 64 Bit on my 80G SSD last night and after it and a few motherboard drivers I was sitting at 47 GB Free on a 72.4 GB (That's formatted space) drive...
So figure about 30G for the OS...I'm not sure you'd even GET Win 7 64 on the 24GB SSD...particularly after formatted size decreases (Remember you don't get the full spec that the HD is rated for). And once you did get it on the SSD, you couldn't put ANYTHING else on it (well used apps, etc.).
One more suggestion: you're showing 4G of RAM, keep in mind the Intel Chips go Triple Channel so you might consider 3x2GB instead of 2x2 (Dual channel is still supported obviously but you'll get better performance (I think?) from triple channel).