CCleaner 64 or 32 Bit - which to use?

CCleaner for Windows
1

I have Windows 7 64 bit. What CCleaner should I use? I just see one version on your website?

2

In short: yes the single version will run fine on your machine.In long:

I have Windows 7 64 bit. What CCleaner should I use? I just see one version on your website?
The fact you only see one version is because there only needs to be the one version. I'm not sure what your question means exactly, as there only being one version, to me, would answer the question itself.
3

The installer installs both x86 and x64 on the machine as needed and opening the 32 bit version on a 64 bit machine automatically opens the 64bit version.