Yes you can partition it to two drives of 60 and 100Gb.
Yes you can copy your stuff onto the 100Gb partition.
Yes you can then install windows onto the 60Gb one.
Yes all of your stuff will be seen on the drives. However if you format it to NTFS you must be running Win 2000 or Win XP to see the drive. If it is formated to FAT then any version of Windows will see it.