If you have a bunch of Microsoft Office templates that you love, you can just choose File > Open in OpenOffice.org to use them. However, if you want them to be available in the wizard when you create a new presentation, or available from File > New > Templates and Documents in OpenOffice.org, you need to do two things: convert them to OOo format, and put them where OOo expects to find them.
Converting Your Microsoft Office Templates to OpenOffice.org/StarOffice Format
You need to convert them to OpenOffice format. Choose File > Wizards > Document Converter. Follow the wizard through to create a converted set of copies of the templates.
Click OK, and OK, and OK again.
Pointing to Templates to Use: Approach 2 (Usually Need to Do This for Impress)
1. Copy the directory of converted copies.
2. Paste it into this directory:
openoffice\share\template\en-us (or whatever your language is)
3. If they don't show up in the wizard, restart OpenOffice.org and your computer if necessary
If You Only See One of the PowerPoint Templates That You Converted, in the OpenOffice Wizard
See this entry.
For More Information on Templates
For more information on templates, see this post, which includes this information.