The window regulators are a known problem with these cars. I have replaced both of mine/DIY. My recommendation is to bite the bullet and pay for the OEM parts. I tried the URO regulators and had problems. There are also several micro switches that work together with the top and windows that can be faulty.
Here are a couple of links that should help;
Porsche Boxster Window Regulator Replacement / Window Switch Replacement / Window Motor Replacement - 986 / 987 (1997-08) - Pelican Parts Technical Article
Porsche Boxster 986/987 (1997-2004) Technical Articles | Pelican Parts
Welcome and safe travels.