I see no reason why not, of course you can't have both set as the default
browser but you can choose which it is (I hope).

You do need IE to access the windows update site, which you should do
regularly unless you have automatic updates turned on. If the Yahoo one is
based on IE (some are and some based on the Netscape browser) it might work
for windows update too, but others probably won't.

You can visit www.charlietame.org and the bottom of the page will tell you
what your browsers sends to a website to identify itself.

This is what IE6 sends...

You are using Microsoft Internet Explorer 4.0 (compatible; MSIE 6.0; Windows
NT 5.2; SV1; SALT 1.0.50414.1 0111 Developer; .NET CLR 1.1.4322; InfoPath.1;
.NET CLR 2.0.50727)

And this is what Firefox sends

You are using Netscape 5.0 (Windows; en-US)

As you can see they are quite different.

Charlie

Yes, and I have Mozilla Firefox 1.5 as my default browser, plus Moziall
1.7.12, Opera 8.51, and even Netscape 7.2 (which never gets used); but...

The SBC Yahoo! Browser is just a branded version of MS Internet Explorer.
Has some extra bells and whistles, but Yahoo! can track your surfing
habits. Even if you don't go to the SBC Yahoo! portal to start surfing.

Out of reflexive habit, I have never installed ISP software on my computer.
And I have SBC Yahoo! DSL Service. BTW, do you know that our ISP has a new,
official name as of Jan. 1?  AT&T Yahoo! HSI.

http://www.dslreports.com/forum/remark,15143952
http://www.sbc.com/gen/general?pid=7582