Excel.exe /Safe

          "C:\Program Files\Microsoft Office\Office\Excel.exe" /Safe

2) Re-register Excel with Windows.  This command instructs Excel to rewrite all of its "factory default" information to the Windows system registry and re-establish links among the various components of Excel. To re-register Excel, go to the Windows Start menu, choose Run, and enter the following:

If you get a message indicating that Excel.exe cannot be found, you need to enter the entire folder directory path to Excel, enclosed in quotes.  Enter something like the following. Your actual path may vary depending on your installation.

Then, repeat this process using /RegServer instead of  /UnregServer.

Excel will start, write its keys to the registry, and then quit.  Now try starting Excel normally.

3) Start Excel without customized toolbars and menus.  A frequent cause of problems is a bloated or corrupt customization file.  Search your hard drive for *.xlb to locate the XLB files used by Excel. Be sure to change your search options to look for hidden files and folders.  XLB files are used by Excel to store your customized menus and toolbars. Their names and locations will vary depending on your version of Excel and Windows.  When you search for and find these files, move them to another location, such as the Desktop.  Now start Excel normally.

4) Start Excel without Add-Ins.  If you are able to start Excel in Safe Mode, as described above, you should systematically disable add-ins to determine if an add-in is causing your problem.  Go to the Tools menu, and choose Add-Ins. Make a note of which add-ins are checked, and then uncheck all add-ins. Close and restart Excel normally. If Excel starts normally, then the cause of the problem was an add-in.  To determine which add-in caused the problem, go to the Tools menu, choose Add-Ins, and check one of the add-ins that you previously unchecked. Close and restart Excel. Repeat this procedure for each add-in.  When the problem recurs, you will have found the troublesome add-in.  You can either leave the add-in unchecked and not use it, or you can contact the supplier for further advice or an updated version.

7) Start Excel without any COM Add-Ins. This is a two-step process. From the Tools menu, choose the COM Add-Ins item to display the COM Add-Ins dialog. If you don't have a COM Add-Ins item on your toolbar, you'll have to add it. In the COM Add-Ins dialog, uncheck any checked items. This dialog lists only those COM Add-Ins that are set up for your user name. Close and restart Excel. If the problem goes away, you have a bad COM Add-In. Leave it unchecked and contact the author or vendor. The second step is trickier and requires that you  examine and perhaps modify the System Registry. Close Excel, go to the Windows Start menu, choose Run, enter RegEdit and click OK. This will open the RegEdit program, the Registry Editor. First, back up the registry. Click on "My Computer" in the tree view control on the left pane of the screen (you may have to scroll up), and choose Export from the File menu. Enter a meaningful file name, select "All" from the "Export Range" frame and click Save. It may take a while to back up the Registry -- it's a big file. Once that is done, expand the "HKEY_LOCAL_MACHINE" node of the tree-view control, find and expand "Software", then "Microsoft" then "Office" then "Excel" then "Add-Ins". For each add-in listed in the tree-view, right click on "LoadBehavior" in the right-hand pane and choose "Modify". Change the value to 0. Keep a list of which add-ins you change and what the previous value of "LoadBehavior" was. Now exit the RegEdit program. Restart Excel. If the problem goes away, you have a bad COM Add-In that is configured for all users of the machine. Run RegEdit again and restore the LoadBehavior values, one by one, restarting Excel each time. When the problem recurs, you will have found the problem add-in. Leave its LoadBehavior value at 0 and contact the vendor or author.

6) Start Excel without Startup Files.  Search your hard drive for folders named XLStart. When Excel starts, it opens all the files in these folders.  Find these folders (you may have more than one, depending on your version of Excel and Windows), and move the files in them to another location, such as the Desktop. Start Excel normally.  If Excel starts, one of the files in the XLStart folders is the problem.  Add the files back to the folder, one at a time, starting and closing Excel between each file, until the problem recurs. When the problem recurs, you have found the file that is causing the problem. Remove this file from the XLStart folder.

7) Run Detect And Repair.  Excel 2000 and later version have a Detect And Repair tool that can help restore Excel to a working version.  This will replace missing or damaged files that Excel needs to operate properly.  From the Help menu, choose Detect And Repair.  You may need your Office installation CD.

8) Delete Files From Temp Folder.  When the Windows Temp directory becomes cluttered with too many files, Excel may have problems starting up, or may start very slowly.  Open the C:\Windows\Temp folder and delete the contents. Also delete files from the Temp folder in "C:\Documents And Settings\Your User Name\Local Settings\Temp". You can get to your temp directory by entering

%Temp%

In the Run dialog on the Windows Start menu. Close all open programs and delete all the files in this folder.

 9) Check VBA References.  You should check the VBA library references to see that they are intact. Open the VBA Editor (ALT+F11), go to the Tools menu, and choose References. See if any are marked "MISSING". If any references are missing, you have two choices: 1) uncheck the missing reference if you do not need it, 2) Browse for the actual file if you do need it. Excel/VBA needs four core references to function properly. These are "Visual Basic For Applications", "Microsoft Excel NN Object Library", "OLE Automation", and "Microsoft Office NN Object Library", where NN is your version of Excel. If any of these are missing, you should re-register Excel with Windows as described in item 2 above.

Related Articles At Microsoft
The following Knowledge Base articles may be useful:

KB814112
Files on Network Shares Open Slowly or Read-Only or You Receive an Error
http://support.microsoft.com/default.aspx?scid=KB;EN-US;814112

KB280504
XL: How to Troubleshoot Startup Problems in Microsoft Excel
http://support.microsoft.com/default.aspx?scid=KB;EN-US;280504

KB211481
XL2000: Startup Switches for Microsoft Excel 2000
http://support.microsoft.com/default.aspx?scid=KB;EN-US;211481

KB291057
XL2002: Methods for Recovering Data from Damaged Workbooks
http://support.microsoft.com/default.aspx?scid=KB;EN-US;291057

KB179871
XL2000: Methods for Recovering Data from Damaged Workbooks
http://support.microsoft.com/default.aspx?scid=KB;EN-US;179871

KB142117
XL: Summary of Methods to Recover Data from Corrupted Files
http://support.microsoft.com/default.aspx?scid=KB;EN-US;142117