installed xp on a 4gb ssd,with some trimming it takes up 800MB. Adding to that some basic programs, and one serious program which is 1,2GB in size, and my XP is very happily cruising below 2,7GB on a 4GB SSD!
Windows 7 32 bit home edition with no xp legacy support fits nicely within 5GB on an 8GB disk.
If you per se need to have the ultimate edition with legacy support, install ms office, and some vantage benchmarks,as well as several games, I can understand you'll need more than a 40GB SSD drive.
32GB is the bare minimum for normal users. A 40-64GB is perfect for most.
Need more space?
Learn to keep your computer clean and in order!
Documents,video's, and audio files can all go on an external HD if necessary.
For the not-so-multimedia-fanatics, a simple 8 GB SD card can host almost anything they need, and costs next to nothing.
I don't get these guys that say they NEED a 128GB SSD for just running windows! It's just a stupendously stupid claim,and just shows you know very little of computers!