In a dual-boot system(one which has both Windows and Linux installed), Linux is smart enough to provide you access to Windows VFAT/NTFS partitions. But same is not the case for Windows.
Ext2 IFS is a free software(not open source) that allows you to do that. It installs a pure kernel mode file system driver Ext2fs.sys, which actually extends the Windows operating system to include the Ext2 file system. You can download it from http://www.fs-driver.org. The linux file system will appear as a new disk partition in windows.
If you install this software, I would recommend you to make the linux the drive read-only. Windows is susceptible to Virus/Worm/Trojan attacks. I didn’t want malicious files to spread in my Ubuntu partition.