Ah lun1986, you can refer to the first page of this thread. Under the post number #5. If you want to format your EMMC (your N900 32GB), use the command "flasher-3.5.exe -F EMMC.bin -f -R" where EMMC is the "51_2009SE_10.2010.13-2.VANILLA_PR_EMMC_MR0_ARM.bin" file. Then don't forget to flash your phone using the above method as referred to post number 5. For your external memory card, I think there is no problem for you to format it. You can format it using your phone as well. Good luck! I hope it will work for you

Ah lun, pls describe your problem.. Screenshot would do good.. hehe
More details, the better..