Windows does not (and probably never will) natively support HFS+, so the partition doesn't show up at all when booted to Windows XP. MacDrive is probably one of the prettiest and most well-integrated solutions, but $40 to $50 is the price tag.

I searched around a bit, and I eventually found a solution that fits the bill rather well. Erik Larsson's HFSExplorer [alternate link] is a freeware Java app designed to let you browse the contents of any HFS+ drives and partitions installed in your system. In addition to viewing the contents of said partitions, you can even extract files to any Windows-writable disk.