firmware not compatible

[speedrug]

Had to restore and re-jailbreak..Whem i restored, my phone was upgraded to 4.1... now im trying to downgrade but getting a error "getting an erroe message "The iphone "iPhone" counld not be restores becausethe firmware file is not compatible." my phone is a 3G..any advice? the file that im using is --iPhone1,2_3.1.3_7E18_Restore

[Simon]

Does the firmware have a .ipsw extension and a white cube like icon?

[speedrug]

no..juz add it to in properties in the name>?

[Simon]

If it downloaded as a .zip then you need to rename it to .ipsw. Or redownload it using firefox and it should be ok then.