Can I access the other half of a partitioned HD?

If I partition my HD in my MB and install Windows on the other half, can I access files saved on the Windows half when running the Mac OS X half and vice versa?

You can see your Windows files on the Mac, but you can't write to the partition unless it is a FAT32 partition. You can read them, though.

There are utilities to allow you to read and write to the Windows partition from the Mac (and vice-versa). Unfortunately you need one for each way.

The easiest way is to just use keep the files you need on both on a memory stick formatted in FAT32 which both can read and write to fine.

NTFS for OS X from Paragon lets you write to NTFS from a Mac. There is also a free option, but I can't recall what it is called.
MacDrive lets you write to Mac disks from Windows. I haven't tried to use it to see the OS X partition from Windows, though.
Both should be easy to find searching Google.

Hope that helps.