Depends a bit on the filesystem that you're using on windows and on the usb stick. But, assuming NTFS for the former, and VFAT for the latter, you could add two entries to /etc/fstab as follows
/dev/hda2 /mnt/windows ntfs ro,noauto,user,umask=0022 0 0
/dev/sda /mnt/usbdrive vfat rw,user,noauto,umask=0000 0 0
Obviously, you will have to be root to edit this file. Then, after creating the two mount points (i.e. the two directories at /mnt/windows and /mnt/usbdrive) you should just then be able to issue "mount /mnt/usbdrive" to mount your usb stick, and the equivalent for windows.
There is a catch, of course. You need to have both the filesystem and the partition correct, in both cases. The easiest way to do this is to issue fdisk -l /dev/hdx
(changing the x to whichever drive you have your windows on), and fdisk -l /dev/sd*
for the usbstick (after inserting it). The reason for this is that often there is a small 'utility' partition at the start of some drives - unless you've formatted them since buying them.
Good luck !