I've got an old HP computer (with a Celeron 566Mhz), and I recently wiped the hard disk and reinstalled Windows 98. After that, I immediately installed my ISP software, and began the long process of updating Windows 98 via the Windows Update site.
Natually, I had a LOT of critical (and optional) updates to install...but I didn't want to install all of them at once because...with my dialup connection...it'd have taken about three days. So I installed them (in reverse order...oldest first) in blocks of 7-8 MB, more or less. Had no problem for the first couple of update cycles...but now I get a "Thank you for trying to update" message, that tries to point me to a special update page for Macintosh computers. The bottom line is that the Windows Update server now thinks my computer is a Mac.
Any suggestions or fixes for this problem?

Thinks it's a mac???!!?!?!

I take it you rebooted after each critical update that requires a reboot? Many of the Microsoft must be installed on their own, with a reboot afterwards. The next visit to Microsoft Update might even indicate more patches to download and update, as many of those will be patches to the patch you have just installed!

I wrote a tutorial on rebuilding Win98 some time ago when I went through the same exercise. However, I do have broadband so the downloads didn't take so long.

Do you have access to a router (say from a friend) that he's prepared to let you use? If so, you could connect your PC to it by way of an Ethernet cable, and start over. You'd also have the advantage of being firewalled during the process as well.

It's possible that a Trojan got in during your download and attacked your PC. I have seen this happen; a friend of mine took a refurbished, totally unpatched PC and when I tried to do the patches, a Trojan got on and totally messed it up. I had to go right back to the start (I didn't have a firewall on a disc with me so had to download it).

But see if others have got any other ideas first......

Google Windows Update server thinks my computer is a Mac and see how many hits you get.

It's an old problem. It used to be a server issue. Perhaps some of the ideas in this (old) thread would provide the solution:

Windows Update Thinks My OS Is A Mac