[X-Newbies] Upgrading to 10.3.5

[Gen Hadlow Mac Impact Dbn]

Machine is a blue and white G3 300mhz with 256mb ram.

Have upgraded to a 40gb hard drive and put in a Sony CD-Writer.
Installed system 9.2.2 and installed Panther up to 10.3.3
After installing 10.3.5 the machine has a serious kernel panic on start up.

Have had to start again - but only upgrading to 10.3.3

There does not seem to be any outstanding firmware updates required that I
can tell - but this mac does not have a modem so its not possible to tell
from doing a software update.

Is there any other issues that I should look into to fix this problem?

Regards
Gen