I posted on the Apple Tech Exchange but got nothing so I thought I'd try here. I have an old PowerBook 540 which had a wiped hard drive so I did a clean install of 7.5.3 and everything was great, tried to update to 7.5.5 and it died.

- First time I got 'bus error', but I had done the update with Appletalk & filesharing on, so I figured that was the problem
- Second try (cleaned hard drive, reinstall 7.5.3) and I get 'illegal operation'

The errors occur before extensions are loaded so my only option is to boot from a disk and then reinstall the OS (which is tiring since its on 16 floppies). Any help or suggestions would be MUCH appreciated.

You may need to do a low-level format (with Drive Setup). This is the only way I can bypass these errors on machines here in the shop when basic initializtion does not do the trick.

Good luck.

Can you explain a bit more (until Dec I haven't used a Mac since high school - an SE).

If this is a hard drive problem, why does OS 7.5.3 work fine? I will try what you suggest, I don't recall seeing that option on the Drive Setup for the boot disk I'm using (Disk Tools 1). Thanks.

[gene]

I had a 6100/60 that was doing the same. I even replaced HD which was formatted by a third party formatter and it didn't help. I have a feeling that it is the logic board or a part of it. Try resetting it by disconnecting internal battery for 15 minutes.

Thanks - I think the problem might actually be the PRAM, it's dead. I've ordered a replacement and will do this all over again once that arrives.