[SWLUG] confused by rpm

[Dick Bain]

Have a friend who uses yahoo messenger, so I installed ymessenger for 
Mandrake but when it starts it gives a load of gtk error messages before 
starting so I thought I would remove it and start again, however if I type:
[root at debains dick]# rpm -el ymessenger-0.99.19-1mdk.i586.rpm
I get the message:
error: package ymessenger-0.99.19-1mdk.i586.rpm is not installed
and when I type:
[root at debains dick]# rpm -i ymessenger-0.99.19-1mdk.i586.rpm
I get:
package ymessenger-0.99.19-1mdk is already installed

I don't understand what is goung on??
Dick