I have a PC thats on a domain. That PC is used to connect to the exchange server and occasionally to an SQL database. However when the machine connects to the database, the application it opens and connects to database, runs extremely slow.

There are other PCs that connect to the same database, but are running within a workgroup. These PCs run fine when connected.

Any idea why it runs this slow please?

If its MSSQL, and the pc accessing it is on the domain, it will first try and authenticate any usernames/passwords against the domain controller, whereas clients on a workgroup will authenticate against the usernames/passwords stored in that instance of SQL server instead. Hence the delay is probably caused by contacting the domain controller.

Its not the authenticating bit that slows down the machine - although this takes time as well - but when the application opens up and the user uses the application, it runs really slowly and of course the other machines on the workgroup using the same application run fine