Question : Problem: Windows 2003 64-bit Specification

I have a Trial Version of SharePoint Portal which comes with a Trial Version of Windows Server 2003 Enterprise Edition which has a system requirement of 64bits.

My motherboard is Asus P4S800 which has a bus width of 64-bit.

I do want to assume anything Do I COMPLY.

Answer : Problem: Windows 2003 64-bit Specification

If I misunderstood your question and it is not Windows 2003 Server Enterprise Edition 64bit version then the system requirements are listed here

Microsoft Windows Server 2003 Enterprise Edition
Windows Server 2003 R2 Enterprise Edition
Component Requirement
Computer and processor
 133-MHz or faster processor for x86-based PCs; 733-MHz for Itanium-based PCs; up to eight processors supported on either the 32-bit or the 64-bit version
 
Memory
 128 MB of RAM minimum required; maximum: 32 GB for x86-based PCs with the 32-bit version and 64 GB for Itanium-based PCs with the 64-bit version
 
Hard disk
 1.5 GB of available hard-disk space for x86-based PCs; 2 GB for Itanium-based PCs; additional space is required if installing over a network
 
Drive
 CD-ROM or DVD-ROM drive
 
Display
 VGA or hardware that supports console redirection required
 
Other
 Windows Server 2003 Enterprise Edition, 64-bit version is compatible only with 64-bit Intel Itanium-based systems and cannot install on 32-bit systems