Sorry for English but my Russian is very BAD  , So Download the last version from www.mikrotik.com - make an ISO and install what you want. Then find in this topic crack for 2.8.17 - it's a ZIP archive - in it You will find some files - you only need keyman and loader - they usualy in sub archive called XXXX-part2.zip ot .rar . Find a LiveCD knopix Slackware ot whatever you want. Then run it on Mikrotik machine and mount the partition of microtic in some dir. Copy keyman and loader over original files located in /nova/bin/ .... Don't forget to chmod 755 both of them. Then restart mikrotik. This operation may be done with putting HDD of mikrotik on other linux box and mount Mikrotik partition - same as above. 

Then create a key file with name like my.key and this content:

-----BEGIN MIKROTIK SOFTWARE KEY------------ 
BFexRXO6clMs6FnDnJZ7 P2Xd15rBE6yD8MgKZZVh ail0
O8z7GWT+WBiFna7C7h2K blUr8t3YTpFKy3OYBc9o CA==
-----END MIKROTIK SOFTWARE KEY-------------- 

with FTP client you should be able to upload it on Mikrotik box 
when you done - just start a Console in mikrotik and write this: 

/system license import file=my.key

Mikrotik wants to restart itself and then It's licensed. 

This procedure works on 2.8.18 and 2.8.19 I checked myself.

Added at 26.11.2004, 15:17
I want to ask if someone is played Mikrotik more deeply - I don't use Mikrotik for my client - It not fit my needs but I'am interested in some ideas of Mikrotik and specially 

1. PPPoE server - which software they use and is available for Linux saparetly somewhere. 
2. WEB Accounting - you can find this in http://router_ip_addres/accointing/ip.cgi - of course you have to enable accounting first. 

ip.cgi gives NETFLOW information and I have start some kind of accounting for Linux with fprobe or ipcad. but I like the way Mikrotik does - when it list counters the are CLEARED  and your job i only to get numbers in intervals ot 5 min or so and parse the ROWS

If someone knows more on these two plese write