Problem with Online Windows Updates for W98SE

I just finished building a desktop PC consisting of an AMD K6-2/450 MHZ CPU,
256 MB of RAM, a CD-ROM drive, and two Western Digital hard drives of 6 GB
each.

After building this computer and collecting the necessary device drivers, I
installed W98 first edition and then updated it to W98 second edition. After
that I used my copy of the Microsoft Windows Security Update CD of February
2004. No problems of any kind appeared.

Then I went to the Microsoft Windows Update webpage to download and install
any remaining critical updates or Windows updates. During the download and
install process the computer crashed with the following error message:

Error loading user.exe
You must reinstall Windows

Almost immediately after seeing this message, the system powered off.

I investigated this error message, and found that it could be caused by a
damaged DDEML.DLL file, so I extracted another copy of it from my original
W98SE CD. That did not help.

Thinking that possibly the Microsoft Windows Security Update CD of February
2004 was defective, I fdisked my system drive, removed the partition,
created a new partition, formatted it, then reinstalled W98, followed by the
installation of W98SE. This time I did not use the Security CD, but instead
went to the Windows Update webpage again and began downloading and
installing the critical updates.

Again the system crashed just like before, so I went through the entire
process once more of repartitioning, reformatting, and reinstalling W98 and
W98SE. This time I ONLY used the Security CD and DID NOT download/install
any updates from the Microsoft Windows Update webpage.

The result? No crashes, no BSOD, all devices are OK with no yellow
exclamation marks, and the system runs perfectly - even after repeatedly
shutting the system down and powering it back up.

Anyone have any ideas as to the cause of these crashes? Could there be a
conflict between the data on the Security CD and the data at the Windows
Update webpage?

Thank you.