I am trying to figure out why a simple .XLS EXCEL workbook is taking, randomly, 30 seconds to open.

Before answering:

Please, bear mind the following:

Problem symptoms

• Hanging is intermitent and it takes exactly 30 seconds;
• During hanging there is no cpu or disk activity;
• It only happens during workbook load. Every runs smooth after that;
• Windows Explorer.exe hangs on folder, but all other folders, system and applications are still responsive;
• There are no consecutive hangings. I have to wait for while to reproduce this behaviour;
• All workbooks where located on a local drive (C:\BPI);
• The workbook has no macros and no addins;
• Office 2003 is being used for several years;
• The computer is running Windows XP;
• Computer has several network mapped drives, all addressed to main file server;
• Recently, main fileserver was replaced by Windows 2011 SBS Standard Edition

What I have done so far

• I have traced machine Explorer.exe, using Process Monitor, added Duration column, and filtered by Duration > 1. That's is how I found that hanging was taking exactly 30 seconds. For further information, please refer to Oliver Salzburg tutorial.
• Using Process Monitor, I have also figured out than five operations were taking most of sample collecting duration. Looking at sample image below, column Operation below you will notice that one single operation was taking 29 seconds;
• I have tried different workbooks (all of them smaller than 30 KB);
• I have, temporarily, removed all shortcuts on User Document's folder that were pointing to network drives or shares;
• I have runned CCleaner to fix registry issues;
• I made sure that there were no external links on tested workbooks;
• I have reproduced this behaviour for hours;
• I have extensivelly researched for hours on the web;

Process Monitor's collected and filtered data