Normally, you should be able to quickly resize photos using Media tools in SalesPartner. Here's an alternative method which is available in Microsoft Outlook.
1. Open the folder which contains your high resolution images.
2. Use Ctrl+A to select all
3. Right click your selection, and click Send to > Mail recipient
4. Select your desired output image size from the drop down menu.
5. Click Attach
6. Once your image files have finished compressing, a draft email will open in Outlook, with your resized images attached.
7. Select an attached image, then use Ctrl+A to select all attachments.
8. Right click your selection, and click Copy.
9. You can now paste your resized images into a new folder, and discard your draft email.