Here are some suggestions:
1. Along with Jabu's recommendation, PDAJunkie's video found
here may help with Vista.
2. Use a direct cable form computer to the phone, instead of going through the cradle.
3. As it relates to the slowness of WM 6.1, you will find that a properly installed WM6.1 will make your xv6700 run much faster than WM5. The most reliable and faster ROM's I've used lately are: 20924 and 20755. The only install options I put on mine during the build was Imaging: HTC Camera native to Apache and SD Card Drivers: SD Card Only. The rest of the software I use I installed later on an SD card. If you don't have an SD card, then select those applications during the build that you absolutely have to have.
4. Unzip the file I've attached to this post. It will reveal two cabs. One is a battery fix, which will modify your phones registry automatically to improve battery life dramatically. The other cab involves another set of performance tweaks that significantly improve the performance of your phone. Both of these cabs are in the public domain and free of charge to use.
5. Consider an overclocking software such as XCPUScalar (trial
here). Costs $19. If your going to stick with the XV6700, this is a worthwhile investment. You can set it to scale down CPU performance up or down depending on CPU load. For CPU loads of 0 - 15% I set it at 208 Mhz. The phone at idle usually sits in that percentage range. At 208 Mhz, the CPU runs at half the speed of the stock 416 Mhz, which means it consumes much less battery. This along with the aforementioned battery tweak has made a huge difference in battery life for me. The highest CPU setting I use is 520 Mhz, which is about 25% faster than the stock 416 Mhz, and set it to kick in when the CPU has a load of 60% and above. This is fast enough to give you great video and almost eliminates all choppyness. You may be able to set it to a max of 620 Mhz, however, I discovered my phone was locking up too much, needing frequent soft resetting.
Good luck