Here is the 04.04 downgrade firmware in case anyone needs it.
I've mistaken upgraded to 04.04 and the scope reverted itself to DS1052E. because I want to sell it, I'd better have it display itself DS1102E instead of explaining to every potential buyer it's a 100Mhz though it says it's not. After I read
A Hellene 's reply, I realize it is really simply to make you own downgrade firmware as long as rigol don't change the upgrade checking logic in 04.04, which it's no quite possible. Long story short, I copy the 0x00-0x13 hex code to the existing downgrade firmware, copy it to a usb stck then plug it in, the scope prompt confirmation about update. Done.
@AlienRelics