OK, you can install F7 using the FC6 partitions
1. When you get to the disk druid in the anaconda installer it will show sda and sdb with checkbox on the left.
Uncheck sda then
up above is a long button dropdown that ask about what to do for partitioning.
click it and set it to manual / custom.
Then click next and the partition screen will show.
Since you are not using LVM you only need to select each FC6 partition and then click the edit button up above.
You then need to select the /mount and check format for each one (They will all be ext3 except for the swap, set that to type swap and you don't need to format it.)
sdb3 = swap
sdb5 = /boot
sdb6 = /
The next item is very important and don't forget it when don with the partitions,
click the advanced option chceckbox at the bottom of the screen.
At the top make sure it is saying to install the grub bootloader.
then click the next button.
At the top of the next screen it will say where do you what to install the boot mbr - make sure it is on sdb5.
remove the "other" boot entry and select Fedora as default.
clcik next to continue.
On the first re-boot you should be able o select the FC6 boot.ini option and it will take you to the F7 grub menu.
(edit the boot.ini file to say Fedora the next time you are in windows.)
Count yourself lucky for using the boot.ini in windows and using seperate /boot partitons
otherwise you would be facing the end of you linux systems due to grub versions and the next installment of SELinux will relabel the /boot partition in F7, which FC3 may not like.
good luck, .. I mean more good luck