Absolutely - but you need a PC with a CD, a supported Network card, optionally a crossover ethernet cable or a switch.
Download the Cobalt OS Restore CD from
http://javashoplm.sun.com/ECom/docs/Welcome.jsp?StoreId=8&PartDetailId=Sun_ Cobalt-restore-G-F&TransactionId=Try
Burn the downloaded image onto a CD-R (or -RW) and boot the PC from the CD.
The PC will then tell you what to do on the 550 to boot from the network - do that and then go get a coffee.
Remember to back up all your non-recreatable data before you wipe the 550.
Good luck!