Question : Illegal operation

My window sometimes freezes and have sometimes error messages saying "Illegal Operation" After I did some things that I was reluctant to do as follows: I downloaded some demo games which are over 50mb long; I installed some source code and java class in Frontpage 97 advanced editing software that came with the used, old book Frontpage 97 Unleashed--I, though, have Frontpage98 installed in my computer--during the installation, it said that My Autoexec.bat will be replaced to something I don't recall and Autoexec.bat will be backed up by Autoexec.001 or Autoexec.002.
 I got an illegal message when I clicked on System Information (shortcut to program\common files\microsoft shared\msinfo\msinfo32.exe)--kernel32.dll was stated in the msinfo32 warning. I ran Inbox Repair Tool, it found 2 errors and fixed, it said. But it itself freezed.
I clicked on System Information again, but now it says "Msinfo32 is not a valid Win32 application." I reinstalled my Office 97 pro. All the applications encountered illegal operation warning! I warm-booted several times and did scan-disk and defragmented. Then I fortunately didn't see the devil illegal operation warnings as much. And actually I rarely see the error messages. Then out of curiocity, I clicked on System Information again. It was working BUT IT DIDN'T HAVE AS RICH TOOLS AS PREVIOUS. IT LOOKED LIKE IT IS MSINFO16.EXE! I THINK IT ACTUALLY IS. So I ran the Inbox Repair Tool again. It says also it fixed. It also freezed itself. Then I got the same message as above, "MSINFO32 is not a valid Win32 application."
During the mishabs, I deleted the Java class and source code and the downloaded game demos.
What's wrong with my computer? I had even some underlines next words on message box on some applications like asymetrick 3d or frontpage 98 editor when I tried to close a work in it without saving it. This was happening even before I did those things.
I think that a thing(?) is trying to stop me from running MSINFO32.exe which is Win32 application.
What should I do? I  know I have a lot of questions.  

Answer : Illegal operation

yongsiklee, the rules would apply here if there were one question and one answer, however you have had many questions and were given many answers. Given the fact that you have added and deleted many software items, it may be impossible to point to a specific cause for your problem, however I was willing to work through a few of them in an attempt to improve your system. I still feel that you may have some components that may not work well together, however with all of the software changes you have made, that may be impossible to determine without first checking the Windows 98 compatibility list, making sure that the two video cards will work together and then making sure you have current drivers and then reload windows 98.