Please send me over to the Virus forum if I'm not in the right place...
To cut a long story short, using various antivirus/antispyware tools I've rid myself of various trojans.
One of these attached itself to netbt.sys. I've restored this from c:\i386, but nothing I do can get DHCP to start up.
Services gives error 1075: the dependency service does not exist or is marked for deletion.
Event viewer shows event id 7003: The DHCP Client service depends on the following non-existent service: netbt. Next message has the same dependency for TCP/IP NetBIOS Help service.
Thanks for reading and hope you can help - I've tried everything I could find on google.