ASP.NET 3.5 on IIS7.5 application pool issue

Knowns:

1. Website hosted on IIS7.5 on 2008r2 server.
2. Website created in VS2008 using .NET3.5
3. If Enable 32-Bit Applications in Advanced Settings for Applications is changed to false it is inaccessible. If set to true it is accessible.

Unknowns:

1. Why 32-bit process AnyCode website cannot use 64-bit ODBC.
2. Why 64-bit process AnyCode website doesn't open.

I have not found any settings to set to x64 compilation through searching this forum and the first 7 pages of google. Only applications seem to allow this websites are listed as .NET and are apparently "bit-less". If they are "bit-less" why does it not work under both true and false?

When running under the true the website works as expected apart from not being able to access the 64-bit ODBC driver. I presume that a 64-bit process would allow 64-bit ODBC access but as that fails I cannot prove this.

There seems to be no concrete information on this and I cannot be the only person that has hit it. Any ideas?