Installed Live Messenger on XP SP3, but only Messenger 4.7 starts

I recently downloaded and installed Windows Live Messenger
14.0.8050.1202. It installed with no glitches and ran the first time for
an extended video call. The video quality was great -- better than
skype. The next day, I tried to start it by clicking on the Windows
Messenger icon in my programs, and the old version (4.7.3001) started.
It doesn't even have capability for video calls!

What can I do to get the new version to run, and to get rid of the old
version?

I'm running Windows XP Home 2002 version, SP3, on a 2.8 GHz Celeron with
2 Gb RAM. I connect via network through a linksys wireless/wired router.

You have to remove (control panel->software->Installed Windows software)
the messenger, which is part of WinXp first, before installing WLM.

only I am not that experienced with this,
and am not sure what you mean.

Do you mean Control Panel --"Add or remove Programs"? If so, there is
no Windows Messenger listed in that list.

And there is no "software->installed Windows software" in the control
panel . . . .

You answered your own question. You have to start Windows Live Messenger,
not Windows Messenger!

Yes, I meant "Add or remove Programs". In the Dutch version it is called
"software".
But if you see this list, just look at the left part (next to the listed
items) and there is
a button (third from above) called "Add or remove Windows-parts".
Click this and you'll see another list with programs, which have
check-boxes.
The last one is Windows Messenger. Probably this one is ticked. Remove
the tick and then
the "next" button, etc. etc. This will remove the built-in Messenger.

Anyway, problem solved. Here's how:

go at control panel-->add/remove programs-->and choose "add windows
components in the left-hand pane. Uncheck windows messenger. Restart.
Now, the downloaded Windows Live Messenger appears on the program list,
and it functions properly.

Thanks to all those who offered suggestions.

I tried uninstalling Windows Messenger, but it just won't uninstall.

The instructions here won't remove it, it'll just hide the icon.

Any particular reason you wish to remove it? In up-to-date XP nowadays, Windows Messenger is
best left just sitting there off on its own unused.

If you really feel the need to get rid of it, you can do so correctly by clicking the Start
button, then clicking Run and put into the field:
RunDll32 advpack.dll,LaunchINFSection %windir%\INF\msmsgs.inf,BLC.Remove
Then click OK.