I installed CiviCRM 1.5 with Drupal 5.0 following the same steps I took installing it with Drupal 4.7 and got no errors.
CiviCRM wouldn't show up in the modules list in the admin section, so I poked around a bit to see what the overall setup was of the Drupal 5.0 modules.
I moved the civicrm.css file into the main civicrm folder, moved the civicrm.module file into the main civicrm folder and then created a civicrm.info file and follwed the same format as the other .info files (a couple of lines of code describing the module) to write to the civicrm.info file. I copied the civicrm.settings.php file to drupal/sites/default folder and went back to the Drupal 5.0 admin area and lo and behold, CiviCRM 1.5 was there. I enabled it and it worked.
The link to my test Drupal 5.0 site with CiviCRM 1.5 is here:
Based on the adjustments I made it would take all of 15 minutes or so to throw together a CiviCRM 1.5 package for Drupal 5.0
Note that our goal is to make CiviCRM v1.6 compatible with Drupal5. I suspect CiviCRM v1.6 will be released before Drupal 5, so we'd recommend u use v1.6 which has quite a few new features and bug fixes etc