DV transfer takes huge amounts of a PC's resorces so.....
Stop ALL background programmes. I use a programme called EndItAll (do a search on Google etc.) and this does it all for you. This prog. is a free download
Make sure your screensaver/powersave are all disabled.
Defragment your Hard Drive.
You say you can capture OK, so I assume that you have DMA enable for your disk.
Also, why copy the file to a DV tape? Just use the camcorder as a DV to analogure converter. Saves a lot of stress on the camcorders heads.
Mark.