i started installing today

i followed this guide to install and configure PHP 5
http://peterguy.com/php/install_IIS6.htmland it was succuess (i think- atleast phpinfo was working nice)
(it shows connection to MySQL server via mysqli)
MySQL was real easy to install
i started with the Bigace_2.7_beta.zip from the nightly build page
extracted the zip and install.php file to my webroot folder.
when browsing to install.php i noticed that the second install path did not have any / or \ in it
and then the files wont extract
Errors:
Could not create directory: C:\Inetpub\wwwroot/addon/
Could not create directory: C:\Inetpub\wwwroot/addon/FCKeditor/
Could not open file for writing: C:\Inetpub\wwwroot/addon/FCKeditor/_upgrade.html
Could not create directory: C:\Inetpub\wwwroot/addon/
Could not create directory: C:\Inetpub\wwwroot/addon/FCKeditor/
Could not open file for writing: C:\Inetpub\wwwroot/addon/FCKeditor/_whatsnew_history.html
Could not create directory: C:\Inetpub\wwwroot/addon/
Could not create directory: C:\Inetpub\wwwroot/addon/FCKeditor/
Could not create directory: C:\Inetpub\wwwroot/addon/FCKeditor/editor/
Could not create directory: C:\Inetpub\wwwroot/addon/FCKeditor/editor/css/
Could not create directory: C:\Inetpub\wwwroot/addon/FCKeditor/editor/css/behaviors/
Could not open file for writing: C:\Inetpub\wwwroot/addon/FCKeditor/editor/css/behaviors/disablehandles.htc
Could not create directory: C:\Inetpub\wwwroot/addon/
etc
so i did an manual extract
Errors:
Could not open file for writing: C:\Inetpub\wwwroot/addon/FCKeditor/_upgrade.html
Could not open file for writing: C:\Inetpub\wwwroot/addon/FCKeditor/_whatsnew_history.html
Could not open file for writing: C:\Inetpub\wwwroot/addon/FCKeditor/editor/css/behaviors/disablehandles.htc
Could not open file for writing: C:\Inetpub\wwwroot/addon/FCKeditor/editor/css/behaviors/showtableborders.htc
Could not open file for writing: C:\Inetpub\wwwroot/addon/FCKeditor/editor/css/fck_editorarea.css
Could not open file for writing: C:\Inetpub\wwwroot/addon/FCKeditor/editor/css/fck_internal.css
etc
i guess i have some permissions issue
Since this is an INTRANET server i gave IUSR_<servername> modify permissions om my webroot folder... and the install.php would countinue
(this setting would also allow the installscript to extract the zip file from the beginning)
All green dots exept "Magic Quotes GPC" and "Apache Header"
Click next and fill in MySQL data ... select "not possible" at Rewrite and .htaccess
Database Created (checked with MySQL-Front)
click next and then i got a http 500