You expect CRT and Xmanager to work in release 7? I wouldn't expect anything GUI that worked under release 5 to be still supported in release 7. You probably have 10 or more years of development progress in-between.
I suggest to check /var/log/messages and Xorg logs. The software acceleration message is only a warning and may indicate that your PC hardware isn't fully supported. But there is simply no information here to pin the culprit.
But why bother with a GUI for the purpose of installing Oracle database, etc. You do not need to run a X window server on the Linux box to have a remote GUI. My suggestion would be to use Tiger VNC, or ssh -X forwarding. For a Windows client, free mobaxterm should be useful, which is a single application that provides what you need. Simply ssh -X into the Linux server and start the Oracle runInstaller and do not set any DISPLAY variable.