This will save the image in its original resolution (if you just cut and paste you’ll get a PowerPoint altered, lowrez version):
PowerPoint XP, 2003 and 2007:
- Right-click the image, choose “Save as image” from the pop-up menu. The Save As Picture dialog box appears.
- Select a location for the picture and give it a name
- Click the downward-pointing arrowhead next to the Save button and choose “Save original”.
Source: www.pptfaq.com