heres how to mount the .fs files with read and write. that means you can add stuff to your sdcard the easy way.
first you need to put windows 7 into test mode heres how:
1. Download http://files.ngohq.com/ngo/dseo/dseo13b.exe
2. run as administrator
3. change windows to test mode
4. restart pc and contunue on
now the fun stuff:
1. Download the Ext2 Driver for windows from: http://www.sourceforge.net/projects/ext2fsd
2. install the drivers. be shure to check ext2 write support or something like that.
3. download gizmo drive software from here: http://arainia.com/software/gizmo/overview.php?nID=4
4. install gizmo drive software
5. restart pc
6. turn off bluestacks service
7. go to C:\ProgramData\BlueStacks\Android
8. rename the file extension on whatever .fs file you want to mount to .img
9. open gizmo drive and mount the file you just renamed
10. it will be mounted like a thumbdrive and you can mess around with it.
11. when you are done unmount the .img in gizmo drive
12.go back to C:\ProgramData\BlueStacks\Android
13. edit the file that you changed to .img back to .fs
14. restart bluestacks service and open up bluestacks to see the things you have changed.
after the initial setup to continue to mod the files later repeat steps 6-14