Edit 2: Don't read the following, Mac, unless you want a good laugh.

I finally installed IE8 last night and had the following problems on my dual cpu 600 MHz PIII, 1 GB RAM, XPSP3 computer:
- IE8 repeatedly took 60-85 seconds to load.
- the Java automatic update checker, jusched.exe, would occasionally grab 50% cpu for for up to 20 seconds. It normally uses none.
- Google's gmail notifier, gnotify.exe, would use 50% cpu for 40 seconds just to load and get to its password prompt. This is while IE8 wasn't running.
I've uninstalled IE8 now and everything's seems to work properly again. Oh wonderful, I see it's left behind some Errors for the XP Event Viewer to report[1]. A web search might help me figure out how to address those. Seems like most of the other vendors can push new versions of Internet software without horking my machine, but this one didn't.
I checked the minimum system requirements:
* 233MHz processor or higher
* RAM: 64MB for Windows XP
I pity the poor fool who believes them. There are other browsers that run well on a system that old, but IE8 does not appear to be one of them.

Thanks for listening.
[1] Windows cannot query DllName registry entry for {CF7639F3-ABA2-41DB-97F2-81E2C5DBFC5D} and it will not be loaded. This is most likely caused by a faulty registration.
Windows cannot query DllName registry entry for {7B849a69-220F-451E-B3FE-2CB811AF94AE} and it will not be loaded. This is most likely caused by a faulty registration.
Edit: Found fix and deleted the two empty registry keys.
http://support.microsoft.com/kb/957700/After you uninstall Internet Explorer 8, you may notice Application event log errors after each reboot. To resolve this problem, delete the following Internet Explorer User Accelerators and Internet Explorer Machine Accelerators registry keys in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\GPExtensions:
{7B849a69-220F-451E-B3FE-2CB811AF94AE}
{CF7639F3-ABA2-41DB-97F2-81E2C5DBFC5D}