Well, I know you are not running Windows XP, so I am going to guess you have Windows 98 (most likely) or possibly 2000.
My first suggestion would be to reinstall Internet Explorer. Although there is no way to do this by conventional means, there are some not-so-commonly-known ways to do this.
First, if you are using Windows 98 you can do the following:
Start / Run /
Type msinfo32 and press Enter .
Click on Tools > IE Repair Tool and hopefully that will repair your IE installation.
If you are using Windows 2000, this may work (although doesn't always).
Start/Run
Type: rundll32.exe setupwbv.dll,IE5Maintenance
Worst case scenario is you can reinstall IE5.5 from the Internet. This only works properly if you have an older version.
Windows detects your IE version and if it is the same version - Refuses to install. If it does this, I know of a registry trick that can get past this in XP (should work with 2000). Please ONLY attempt this if you feel comfortable working with the registry. Backup recommended!
Start/Run/Regedit [enter]
Navigate to: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components\
Then look at the last keys (folders) in this section (should start with a > sign ). Check each of thekeys with > in front of them.. One should contain the ComponentID string with the value "BRANDING.CAB" in the right-side pane.
You will want to delete this whole key (folder) (>{60B49E34-C7CC-11D0-8953-00A0C90347FF}MICROS for example).. But your number will be different, so don't go soley by that. That's just my current number.
You should now be able to install IE5.5 without Windows being able to detect your IE version.