If your GUI object is mounting ro then you have a couple of options:
1. With most GUI-based mount tools you can right click on the disk icon, choose Action and Change Read/Write Mode, then select the Read/Write option (doing this from memory, so the option names may not be correct).
2. Open a terminal window and type "mount -o remount rw /mnt/hda2" and Linux will remount the drive with read/write permissions. You must do this as root, so if you are using one of the LiveCDs you will probably have to append "sudo " to the beginning of the command.
The reason that you are probably having difficulty unmounting the partition is that you probably have a Konqueror window open that is displaying that directory. If any application is working in that directory (or sub directory) you will get that unmount error.
pansophic