Document – System Requirements: Hardware

CPU Speed:
1.0 GHz recommended or higher
Processor:
Intel Pentium or Intel Xeon Processors
Memory/RAM:
512 MB minimum, 1 GB recommended or higher
Display Color:
Greater than 256 color depth
Disk Space:
352 MB NTFS
Notes:
ArcGIS Server .Net ADF 9.1 is supported on the following web browsers: Internet Explorer 6.0 and higher
Netscape 7.2

Visual Studio .NET Requirement
- Visual Studio .NET 2003 and .NET Framework 1.1 Service Pack 1

Additional Notes:
- .NET Framework 1.1 is installed with Visual Studio .NET 2003. The redistributable is available to developers who want to include the .NET Framework installation with their .NET applications.

Limitations
Web Server: The .NET ADF is not supported with Solaris or Linux based ArcGIS Server Objects.

From ESRI Support Website
.Net ADF 9.1 with PC-Intel Windows Server 2003 on Internet Information Server 6.0