How can I create and access more partitions in a pendrive in Windows 7?
I found the solution for me in this question! A small application that alternates the first partition without having to reboot.
Long story short, you download and run Bootice, go "Parts Manage" > select your new first partition in the table > click "Set Accessible" and it's done already! After that you can just click close and exit.
I found this forum post which appears to point to a 64-bit compiled driver. I think this is what you're looking for. Please, take appropriate caution when downloading random files et cetera.
For the record, my Google search term was:
removable drive bit x64, and that showed up near the top.
If Windows disk management as suggested above doesn't work then try http://www.partition-tool.com/personal.htm its free but upon installation avoid installing crapware! (read the prompts carefully) I usually multi-partition my usb drives under linux w/ cfdisk, afterwards they work under MAC & Lin but my 4 partition beast has problems under Windows XP :(