Hi and welcome to the forum
First question is does your Win7 Pro have SP1 (Service Pack 1) installed? If not, you should install it, as there are many bug fixes there for outlook.
Next question is do you have SP3 (Service Pack 3) installed for Outlook2003? That software is now 13 years old and needs to be patched in order to work correctly. This should also be installed.
Prior to attempting any repairs to your PC you should
MAKE CERTAIN THAT YOU HAVE ALL YOUR PERSONAL DATA (LIBRARY FOLDERS) BACKED UP TO EXTERNAL MEDIA TO AVOID IRRETRIEVABLE DATA LOSS!!!.
Assuming there are no hardware issues with your computer, I would next run the Office2003 built-in repair tool. There were 2 repair tools; 1 runs from inside windows, and a 2nd tool you could download from Microsoft. Here's a link to using the 1st tool:
How do you use the inbox repair tool (scanpst.exe) for Outlook 2003? I am not able to send and receive emails..
The 2nd tool that was online has been removed since Microsoft end-of-lifed all support for Office2003 quite a while ago:
Link Removed.
If this doesn't work, you should attempt to uninstall Outlook2003 from Office2003 using the Win7 control panel-->programs and features applet.
Make sure to temporarily disable your AV or antispyware programs otherwise this process will fail! Choose uninstall Outlook only; and then reinstall Outlook only. Retest for your problem. If fixed; you're done.
If problem persists, repeat this same procedure and uninstall
ALL OF OFFICE2003, and reinstall. Retest for your problem. If fixed; you're done.
**NOTE: In many computers, the uninstall Office module or uninstall all of Office options may require you to have your original Outlook 2003 disc in the computer in order to run these procedures. This is very critical!!
To answer your original question, there is no formatting for the nav bar in Outlook2003; you can adjust the width of the nav bar, and you can increase or decrease the font size of your windows screen which may allow more or less text within the nav bar. You should check the screen resolution of your computer; e.g. 1024x768. Sometimes different programs such as games on your computer will ask you to reset your screen resolution, and of course this will affect how much text can be placed in the width of the nav bar. I suggest you reset your screen resolution to it's original size. If you don't remember that, use the
"defaults" button to reset it to whatever setting windows was using when you installed it originally. Try this and retest for the problem. If it goes away, you've fixed it!
There are additional issues that could be causing your Outlook to misbehave, and the #1 cause of all failures in computers with Win7 on them is the hard drive, due to aging failures. If your computer was built in the XP-era (2001-2006) or the Vista-era (2007-2009), this is even more likely if you upgraded a computer this old to Win7 or paid someone to do it for you. It would help us to know at least the Make/Model of your computer and whether it's a desktop PC or a laptop? Hard drives are only designed to last 3 years in desktop PCs, and only 2 years in laptops. Your computer is at least 7 years old if running Win7 and it came that way from the factory. It could be as old as 15 years old if you upgraded an XP-era computer to Win7!
Running 13 year old Outlook program on a 15 year old computer, you can imagine there could be multiple failures both hardware and software.
Next things to consider are these items that are likely to cause a software-like failure such as you are seeing:
1.) Virus/Malware infection
2.) Hard Drive failure
3.) Windows System file/registry corruption
To remedy these you'd have to do the following:
1.) Run the AV program installed on your computer; scan/remove all viruses found. Retest for your problem.
2.) Run Hard Drive test diagnostics to test the integrity of your hard drive (post back for a link).
3.) Run software repair tools to correct the corruption in your windows (post back for a link).
These are the things that I would attempt, in order, to try and fix your problem. I've seen this before, but due to the age of your computer (guessing!), it's very likely if the first few things don't fix it at the top of this post, you've suffered a hardware failure that's causing your Outlook2003 to misbehave.
If you have no other symptoms such as other programs misbehaving or not displaying correctly, this could be an early indicator your hard drive or RAM stick is failing. Not surprising on such an old computer.
Post back answers and results of the solutions we asked you to try, and we will advise you further.
Best of luck,
<<<BIGBEARJEDI>>>
It sounds like you know what you are doing. 
