Well the Athlon 64 3700+ is an expensive but high-performing CPU, whilst the Celeron D is a cheap, but low-performing CPU.
The Celeron D won't beat it at anything, really. No point getting a Celeron D 2.93GHz. Semprons are far better.
And just to make it clear; the speed of a CPU is NOT related to clock speed...unless you're talking about, say Pentium II's and K6-II's.