User Null modem cable and check the console output from the router,
http://wiki.mikrotik.com/wiki/First_time_startup

If you have problems post the output from the console here.

me too.
also I try press key within 2s but no any other result.
below is mine in console windows.
RouterBOOT booter 2.20

RouterBoard 433UAH

CPU frequency: 680 MHz
Memory size: 128 MB

Press any key within 2 seconds to enter setup..
loading kernel from nand... OK
setting up elf image... OK
jumping to kernel code
Kernel panic - not syncing: No init found. Try passing init= option to kernel.

I solved my problem.
the keypoint is that 433 use a pushbutton to select boot way.
press that button with power-on then I can see I want to see.
this is the important information I want to share.
then it is OK to follow netinstall wiki.

Hi
I have 433ah
when i connect the power LED 501-504 is burn and blue and green LED on too.
board did`t startup.
in hyper terminal did not write anything
Sorry, my English is bad

Hi, I have the same problem

RouterBOOT booter 2.6

RouterBoard 532

Authorization: Passed
CPU frequency: 266 MHz
Memory size: 32 MB

Press any key within 2 seconds to enter setup..
loading kernel from nand... OK
setting up elf image... OK
jumping to kernel code
Kernel panic - not syncing: No init found. Try passing init= option to kernel.

It's not clear how to solve the problem, I need help, please

Make fresh installation with Netinstall, it seems there is problem with FS on flash and I suppose there is risk that you have lost license key.