I chose the Windows XP Pro x64 Edition for my new working machine, a DELL Precision 380, as long as it has an Intel EM64T processor.

Having bad luck, after installing .NET 2.0 Beta 2 Redist (x64), IIS 6.0 and Visual Studio 2003 one by one, I got errors in Visual Studio 2003 when creating new ASP.NET Web Application project. It took me about two hours painful time to figure it out. In short, root causes are 1) the coexistence of .NET 1.1 & 2.0 and 2) the x64 OS.

Summarize my findings as below for upcoming developers:

Error 1: You may see an error message like "Visual Studio .NET has detected that ASP.NET applications and services are locked down in IIS. You can run the IIS Security Lockdown Wizard to change lockdown status" when creating a new ASP.NET project in Visual Studio 2003. This is caused by the coexistence of .NET 1.1 and 2.0.

Solution: 
(i) Go to the folder C:\WINDOWS\Microsoft.NET\Framework\ and run "aspnet_regiis.exe -u".
(ii) Go to the folder C:\WINDOWS\Microsoft.NET\Framework\v1.1.4322 and run "aspnet_regiis.exe -i"

If still no happy, move on to check "Web Service Extensions" in IIS manager (run inetmgr in "Run...") and set "ASP.NET v1.1.4322" to Allowed, if it's Prohibited.

Error 2: You may also see an error message like "The Web server reported the following error when attempting to create or open the Web project located at the following URL: 'http://localhost/AuthorsWebService', 'HTTP/1.0 503 Service Unavailable'" when creating a new ASP.NET project in Visual Studio 2003.

Solution:
Go to http://go.microsoft.com/fwlink/?LinkId=39058, download and install the patch (it's x64 compatible). After patch installed, run "cscript %SystemDrive%\inetpub\AdminScripts\adsutil.vbs set w3svc/AppPools/Enable32bitAppOnWin64 1" in command line.

So, to avoid the painful troubleshooting as mine, strong suggest .NET developers:
1) Install .NET 1.1 and Visual Studio 2003 on 32bits version Windows XP;
2) Install only .NET 2.0 and Visual Studio 2005 on Windows XP x64 Edition.

Plus, on WinXP x64, you don't need to install Front Page Server Extension before installing Visual Studio 2003. FPSE is built-in and you cannot find any entry for FPSE in Add/Remove Windows Components on WinXP x64.

Btw, WinXP x64 only support SQL Server 2000 SP4. SP3 is incompatible.