I'm a newbie working with Red Hat 8.0, i just upgraded from 7.2...

Everything ive installed has gone smoothly. Yet i am now trying to install mplayer and with the .rpm it gives me this error:

[bacon@pcp986871pcs bacon]# rpm -i mplayer-common-0.90rc4-2.i386.rpm
warning: only V3 signatures can be verified, skipping V4 signature
package mplayer-common-0.90rc4-2 is already installed
[bacon@pcp986871pcs bacon]#

and with the .tar file it gives me:
[root@pcp986871pcs bacon]# tar -vxzf MPlayer-0.90rc5.tar.bz2

gzip: stdin: not in gzip format
tar: Child returned status 1
tar: Error exit delayed from previous errors
[root@pcp986871pcs bacon]#

neither of which mean anything to me. so if you could put up with my inexperience and help it would be greatly appreciated.

surely "package mplayer-common-0.90rc4-2 is already installed" speaks for itself. is mplayer not there already? try running the command.

as for the second one you are usign the wrong command, if you read the tar manpage, the mplaeyr insatllation docs or any linux beginners guide you'll see you want jxvf not zxvf, z = gzip, j = bzip2.