Major FreeBSD Problem plz help

[Jonathan]

Hello, I messed something up in my FreeBSD-5.2.1 box. I ran sysinstall 
in root and installed compat4 and some other compatibility base dir 
thing and it extracted over / i think and now the box wont recognize my 
logins. I am locked out of my own box. Is there a way to reset what I 
did so i wont lose any data. My server is colocated at a datacenter and 
the techs would have to do it. Could you guys possibly explain what 
needs to be done so i wont lose any data and reset what i did. Any help 
would be greatly appreciated
PoisonDart at optonline.net

Regards,
Jonathan