How to run IIS process (w3wp.exe) as 64 bit process

We ran in the following problem in our system.

We have several reports, built with Stimulsoft. Reports use SQL Server as datasource (instead of stored procedures, SQL code is provided inside scripts).

When we run sql scripts in management studio - each of them runs in 3-5 sec. When then stimulsoft builds report, it takes 20 seconds. That's fine - because reports are cross-tab reports, and it is supposed to be a lot of calculations.

We use Windows server 2008 R2 64-bit. IIS process w3wp.exe runs in 32-bit mode. When we run 10 different reports, each of them increase memory usage of w3wp.exe by 300-400 M. And when it reaches almost 2Gb, the following reports stop to execute.

Any idea how to say w3wp to run as 64-bit process?

Launch IIS Manager and select the Application Pools node. Right click on the specific application pool that your site/application resides in and select "Advanced Settings". There'll be a setting under "General" labelled "Enabled 32-Bit Applications":

Set this value to "True" for to run w3wp.exe as a 32 bit process or "False" to run as a 64 bit process.