Please help: can not run SDK examples(XP 64 bit)

Dear all,

I am using CUDA 2.1 32 bit toolkit with XP 64 bit. No matter I compile the SDK examples with VS2005 or VS2008, I get the following error message:
the cudaSafeCall() Runtime API error in file <>, line 155 : initialization error.

Could someone please tell me how to fix this problem? I haved tried two days but still cannot write a simple “Hello Wolrd” program. >.<