I happens to own a Microsoft Intellimouse Explorer 3.0A optical USB Mouse. It worked ok with my new PC with 64 bit Windows XP - but I wanted to use the left-side buttons to do copy/paste (in stead of having to first mark the words to copy, then move my right hand to the keyboard to ctrl-c, then move my right hand back to the mouse to mark the position to insert the words at, and then move my right hand from the mouse to the keyboard to do ctrl-v. (I do this hundreds of times per hour when I write c++ code).
First I had to get the driver. I typed in "www.microsoft.com" in Mozilla. The new Microsoft-site popped up - with a nice search input on the right top corner. I typed in "Microsoft Intellimouse Explorer 3.0 driver" in the search input box and pressed enter. The response was fast - but totally irellevant. Lot's of technical articles about how to resolve problems. But I needed the driver before I could enjoy the "user experience" with all these nice looking problems. There was no helpful menus or links at all on the page - not even a link back to the frontpage (at least nothing that I cound find quickly), so I had to use the [back] button i Firefox to try again.
I looked for a "download" menu and found none. I searched for "download" on the page, and found only irellevant links. Somehow I managed to get to the "Dowload Center" by following a link to download Windows Media Player. (The link to the Downloads are actualy on the new frontpage - in a box with Microsoft-sites on the top right, but it's located in a way that makes it the last "download" link to find in Firefox Search. I gave up after 5 - 6 irrelevant mathes on the page. (In IE 7 this is the first match to occur. I guess someone has put some effort into this behavoiur. - It's nice to observe that the money I spend on Microsoft products are being used to something useful)).
I found the driver easily from the Download Center. Installation went smooth. It did'nt even require a reboot, and the functions I wanted to activate was available and easy to set up. It even worked without any problems.
But when I pressed the wheel-button in Firefox to open a link in a new page, I got a totally new "experience". The screen was splitted into 8 windows, each displaying one of my running applications. Some kind of novice ALT-TAB feature was activated. But I never asked for that! I've been using windowing desktops since long before Microsoft Windows became popular (including Windows 2.0 and several other early windowing environments for DOS, two windowing systems under QNX, and of course Motif under X/Unix)- so I've had plenty of time to learn how to organize the desktop and find my applications - fast. I opened the Mouse applet in the Control Panel again, but I have no clue how to restore the wheel-button to the original behaviour.
Then, when I started to get irritated, I discovered that the arrow-keys on the keyboard had stopped working. I closed down my 8 running applications and rebooted the machine. But a reboot did not fix the problem this time. The arrow-buttons were still not working.
After removing the Intellimouse driver, and having wasted an hour - my arrow-keys worked again - and Firefox once again opened links in new tabs when I clicked them with the wheel-button.
I guess I have to get a mouse from some other vendor if i want to access copy/paste directly from the mouse.