As an aside *please format your post*; we like to save our eyesight.
That being said; Slackware doesn't hold your hand as much as many other distros. Some people rather enjoy it.
AMSN / K3B / LimeWire are all easily installed on Slackware.
It sounds like you should read the documentation that came with the Yahoo toolbar -- it sounds like you need to prefix the ./configure command.
As for the login issue, if you could attempt to login as your user, then login as root and post the output from the following command:
tail -n 100 /var/log/syslog
This could help us diagnose your problem.