Error 500 indicates a server error, so something in your asp scripts may have gone wrong. To see more details, do the following:
In Internet Explorer, open Internet Options | Advanced and uncheck Show Friendly HTTP Error Messages.
If this doesn't provide more detailed information when you rerun the page, you may need to change a setting in IIS as well. To do so, open the IIS MMC, and open the Properties dialog of your site. On the Directory tab, click the Configuration button and then open the Debug tab. Make sure that Send detailed ASP error messages to the client is checked.
Rerun the page and post any error messages to this list.