RB500 BIOS upgrade
From MikroTik Wiki
Spanish version of this article: RB500 BIOS upgrade (sobre puerto serie)
If there is a problem with booting RouterOS ("starting services ..."), or any other booting problem with the RouterBOARD500, try to upgrade the RouterBOARD firmware with this file:
http://www.routerboard.com/files/rb-2.9/rc32434-2.9.fwf
this can be done from the BIOS of RouterBOARD500 with Hyperterminal `send file` feature. More info in the RB manual: