Can you install Windows 7 on an Intel Celeron?

Yes, the official CPU requirement for Windows 7 32-bit is simply a x86 CPU clocked at 1 Ghz or above.

Any Intel Celeron D meets those technical specifications.

About Windows 7 64-bit, it depends on model of Celeron D : first models don't support x86-64 instructions but the newer models fully support them.