I too have a Windsor AMD 64 X2 4200+ AM2 socket 89W CPU and I will be overclocking it this weekend. I just received my Zalman 9700 in the mail today with Arctic Silver 5 thermal grease. The 9700 is better than the 9500 because the fan is 110mm as opposed to the 92 mm fan on the 9500, so it can move more air across the fins (or move the same air as the 9500 at a slower speed, meaning it'll be quieter). Also, that chrome plating on the 9500 looked suspect to me. I don't have numbers to back me up, but from what I remember from my heat transfer courses, plain old copper is just about the best (unless you want to drop a few hundred on a silver cooling system lol). The chrome plating should make it more durable though, but unless you're constantly fishing around inside your case it shouldn't be an issue.
As for the thermal grease, you want as thin of a layer as you can get that still COMPLETELY covers the entire heat sink. The thicker the layer of grease, the lower the rate of heat transfer. However, incomplete coverage is even worse. The difference between the rate at which heat conducts through the thermal grease compared to the rate of heat transfer from air convection is HUGE. Gaps in the thermal grease are bad news. I'd recommend cleaning the surface of the CPU heatsink as well as the surface of the Zalman heatsink before applying the thermal grease. You want to get off any grease, oil, and minerals by dabbing a cotton swab in acetone (or rubbing alcohol) and gently and carefully wiping off the heatsinks. Make sure the surface is dry, and swab some Artic Silver 5 on the Zalman heatsink, spreading evenly. Then put a very small dab on the CPU heatsink (center) and lock it all in place.
I'll post some numbers relating to temp's of the 4200 before and after installing the Zalman as well as what numbers I get from my overclock. I'll also post any info I get on this fan controller. My CPU is running on an ASUS A8N32-SLi Deluxe motherboard with 2 gigs (dual channel) of Corsair PC2 6400 C4, an Antec TruPower 550W PS, nVidia 7900 GTO graphics card, and a full ATX case with one 120mm front intake fan, two 120mm rear fans, and a side vent.
I'd be very interested in hearing what numbers you guys get from your overclocks. Keep posting!