Help with logging into Ubuntu 9

I messed around with the file permissions (don't ask why) and now I cannot log in. Before I wipe it and start again I wonder if anyone can help.

I can log in but I do not log into the orginal installation (called gig-ubuntu) but colci@localhost.

I was getting originally getting some error messages which I have fixed by changing the permissions, namely:-
users $home /,dmrc file is being ignored etc. and
must be setuid root

Now whenver I try and do anything I get a message
"not allowed to access system configuration"

I cannot access my network and hence the internet

Is there a way to reset ubuntu and put it back to how it was beofe I started messing around?
Thanks

Thanks.

I am not sure what info I can usefully give - if you would like me to post some log files etc. I would happily do so, if you let me know what to post. I have tried the janitor, which shoudl got rid of some depositaries and I have already chmodded and chgrouped as much as I can - I had to do it in the recovery panel to get pas the first error messages. Now I get no more error messages but cannot log in to the orginal instalation and get logged in to this localhost thing which has no network connection.