You need to mention what model of Zaurus you are flashing.
You should go to Trisoft's site and get an original NAND backup file for your Zaurus.
http://www.trisoft.de/en_downloads.htmMake sure you get the correct NAND for your model of Zaurus.
Follow instructions carefully to return your Zaurus back to the original Sharp ROM.
It's also best to use a CF card.
Get a card reader for CF & SD, they're cheap nowdays.
If you had pdaXrom installed, your "Flash" partition may not be the correct size for Cacko.
You may need to read the pdaXrom forum, or ask a question there about returning from pdaXrom to Cacko.
When flashing Cacko, make sure to follow step 11 thru 13 carefully.
This is the section where you re-partition your "Flash"
Below is a paste of Maslovsky's post for Cacko Full,
NOT Lite-----------------------------------------------------------------------------------------
IMPORTANT: This ROM requries a flash partition at least 32 MBytes in size!
Make sure to repartition your internal flash before updating ROM! Installation:
1. Extract the 3 files - initrd.bin tools.tar updater.sh - to the root of your CF or SD/MMC card.
2. Make sure that Zaurus isn't plugged into AC power.
3. Remove battery for at least 5 seconds.
4. Replace battery (replace battery cover, lock cover), plug in AC power.
5. Press and hold the "OK" button on the keyboard.
6. Turn the power on, you should see the Japanese service menu.
7. Now Plug in the Power Cord. (You will get an error if it isn't plugged in!)
8. Select option 4 (flash/update).
9. You then have several options including CF and SD
10. Choose either CF or SD, depending on which media you put the files on.
11. Select "3 NAND Flash Utils"
12. Select "1 Resize root partition"
13. Enter 32 when prompted for root partition size.
12. Flash will be repartioned and Zaurus will reboot.
13. Repeat steps 2-10 again and wait for the menu start menu.
14. Now select "1 Install new ROM" and wait. Reboot your Zaurus when ROM installaiton is complete.
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(Note) On my SL-C3100, there seemed to be one more step:
After step 10, Select Left Box 'Y' for Yes.