Maximum number of concurrent users

Hi

We are using PostgreSQL 8.3.1 version under windows.
We want to know whether there is any limit on Maximum number of
concurrent users.
In specific, can Postgres handle 1000 concurrent queries?
Regarding our Data size,

We have 40 tables and in total we have 2GB data.
We are using normal Pentium Quad core processor, 3GHZ system with 2GB
RAM as Database Server.

Kindly provide your inputs.

Thanks in advance
S.Kesavan
Emmeskay Systems,
Chennai, India.