Now I just checked to see if there was any scheduled job running. Nothing.

If you look at the responses in the stats you'll see it appears in waves.

There are no other websites running on the machine. It is doing nothing else than being a webserver and databaseserver. There are no scheduled jobs in windows or in sql server express.

It is not a resource issue as there is plent of memory free and no disk shredding happens.

The following 3 queries are run against the database 80-100 times a minute when the server is busy:

1. SELECT *
FROM vw_Modules
WHERE   ModuleId = @ModuleId
AND     (TabId = @TabId or @TabId is null)

2. exec dbo.GetModule @ModuleId=378,@TabId=58

3. exec sp_reset_connection

If something is hitting tab 58 80-100 times a minute then you should be able to spot the culprit fairly easy in the logs.

Not that it's a specifc answer to your problem, but if you were using PageBlaster then those queries would not be called over and over again like that.