32 vs 64 bit software

I have a W7 pro 64 bit machine and have been wondering about 32 bit vs 64 bit software lately. I have an Apache/MySQL/PHP package and for some reason, my INSERT INTO continues to fail in terms of not being written successfully to a mysql table. I've used the same code for a number of years on an XP machine and never had an issue. Suddenly on my W7-64 machine, there are no apparent errors,...