If you have DAEMON Tools program group present in Start Menu then run Uninstall shortcut from there and follow instructions.
If mentioned program group does not exist because setup is not complete (eg. due to crash) or you unchecked this option during setup (eg. for security reasons), then locate the folder where you installed DAEMON Tools and run uninst.exe in this folder manually.
If your setup is not complete and not all files were copied due to some crash (so that even uninst.exe is not present) or uninst.exe fails with some error message then just delete all files from this folder manually.
If older version was before 4.06 then also remove System32\Drivers\dtscsi.sys file.
Then reboot your system.
NOTE: DAEMON Tools V4 also uses SPTD (SCSI Pass Through Direct) driver to access cdroms and it is also automatically installed during DT setup. But SPTD is not removed during uninstallation because it may be used not only by DAEMON Tools but by other applications as well and its removal may disrupt these applications.
Nevertheless, if you suppose your problems are SPTD releated you can remove it as specified in this thread My system won't boot after installation of v4, or problems with SPTD.SYS