First try
Go to Start/Run and type in:
regsvr32 RICHTX32.OCX
Click OK
If this fails, use the XP Search feature to locate the file. Then repeat the
above steps using the full path.
For example, if you find the file in C:\Temp, then type in
regsvr32 c:\temp\RICHTX32.OCX
Click OK
Note: It may be necessary that you copy the file to your System32 folder.
If still no joy (or you cannot find the file), then which program are you
running when you get this error? Do you have an installation CD for this app
where you can retrieve this file and copy it into your ..\System32 folder
and repeat the steps at the top of my post.
If you cannot retrieve the file go to this web site where you will find a
copy.
http://www.ryanware.com/runtime.html
Be sure to copy it into you System32 folder.