That client is already there 6.10.18 x64, just that WCG is not ready to accept it in the present form, but reliable birdies have whispered it is coming in the not to distant future in WCG package format, both CUDA and OpenCL support capable. Whether WCG will issue both a x86 and x64 kit I do not know. The version number will then be beyond 6.10.32/33, the presently alpha tested clients. In the case of only x86, you still can get the standard x64 compile for x64 at Berkeley. At any rate, 6.10.18 is fully W7 capable, the present 6.2.28 WCG agent too.

The webmaster has been asked to add the W7 label to the download-again page.