Is it possible to share files between 2 different os on the same computer?

Of course, and it's very easy. The simplest way is to have a shared partition that uses a filesystem both OSs can understand. I usually have an NTFS-formatted partition which I mount at /data on Linux. This will be recognized as a regular partition on Windows and be assigned a letter (D: for example) just like any other.

You can then use it from both systems and the files will be available to both your OSs.

As mentioned @Terdon, it's easy to access an NTFS partition from linux by mounting the needed partition . Also you can access an ext2 ,ext3 and ext4 partition from windows using the ext2explore tool.

Note that you don't even have to create a partition for the file exchange. Your RHEL5 can natively access your Windows partition and read and write arbitrary files from there. If RHEL is configured correctly, your Windows partitions should show up in RHEL file manager's left navigation bar.