VI 3.0 is out of support and is not available for download anymore.
You may consider installing a newer version (3.5 is still available here: http://downloads.vmware.com/d/info/datacenter_downloads/vmware_infrastructure_3/3_5)
Or you might want to contact VMware support if you really need 3.0.
I understand your concern .Some times we need old version for particual application .
But its very tuff to get from vmware portal because of very old version .
please check some site like old version and filehippo