Question : no access to internet from one PC on network - ping works but nslookup doesnt

no internet access from Win2k Pro PC through IE5.
Ping to www.yahoo.com and others resolves to an IP but ns lookup to same www address doesnt work.
Other PC's on network work fine
can ping other PC's on network.
Any ideas??

Answer : no access to internet from one PC on network - ping works but nslookup doesnt

It turned out to be hidden software that the client didnt realise was installed. the software SPECIFICALLY prevented internet access! and by design it showed up nowhere in the system.