Partition scheme and size for dual boot Windows 7 and Ubuntu 9.10 with separate partitions for data and /home

"your partition table seems to me to be almost correct, but I would think about an LVM (it could seems tricky, but I assure you that it will worth the hassle of understanding and using it).

The main reason is: (personal free-thinking :D) ""I think that 20 GB are really a lot for a / partition (if you're not planning to put a public web server or something that could fill up fast your hard drive), and that 25 GB for home are really a few; but what can I do if someday I'll run out of disk space in the root partition?"". And here is where LVM comes in handy: you can take some MB/GB from your /home or from your unused partition and add'em to your root.

Also, I would split / (root) from /boot: the reason is that you can use an ext2 for your /boot and ext4 for your / (root). ReiserFS it's wonderful, and it's very fast and reliable with a great number of little files (and that's journaled too).
Concerning the NTFS data partition, I would suggest you to mount it in /media/data, so to be easy reacheable from inside Ubuntu.

I hope to see what you will choose in the end: and I wish you best luck for your brave project of dual-booting Ubuntu Karmic and Win7 with such an eclectic partition table!

Regards"