The IE6 SP1 installer is still available from MS:
http://www.microsoft.com/en-ca/download/details.aspx?id=1
Of course do be warned that you are using unsupported software that had not received security updates since July 2010.
Why did anyone bother to press that ancient machine back into service? And why did they not just wipe the hard disk and put up a new copy of the OS on it, especially if there's malware on it?
IE5 was certainly rather painful to use. Google did not work correctly under it. Microsoft's sites were just about the most painful to browse.
Owing to some malware on the system hijacking some DNS things and some further DNS misconfiguration I couldn't even get Firefox for a while... but I did eventually restore order to the machine and get Firefox 10 ESR installed on it. (The latest supported version to work on Windows 2000.)