I run BOINC on a number of projects.
Say i run WCG on one computer, and sun Rosetta on the other.
When I search for my username here, which is "chungenhung" it would show 2 entries.
Apparently the two machines have different CPIDs.
How do i fix this?
Both projects have the same email and username.

Also, would the points on two CPIDs be combined whenever this CPID issue is resolved?

You should run both projects on one computer, this way the BOINC client knows they have the same email address and sends the same CPID to both projects. If you run three projects there should be a chain like project A and B on host 1 and B and C on host 2

Ok, so if i put project A and B on PC1, then project B on PC2, would that solve the CPID thing?

Use the same email address on all your projects.

As FilmFreak says, both computers need to be attached to at least one common project. If you attach your WCG computer to Rosetta, you could just run a few workunits then set Rosetta to No New Work.

Yes, that should solve the problem. After you've made the changes, click Update for every project on each computer. Then wait one or two days.