First off, if they are the 2 windows CDs from the same box (ie share the same license) it cannot be done. But you can try to follow these suggestions to see if it helps your cause, and if you own 2 separate licenses: How to install Windows 7 32 bit and 64 bit with dual boot - Microsoft Answers
May I suggest that if you have 4GB RAM or less, using ONLY the 32 bit (also called x86) one, and if you have more than 4GB RAM, using ONLY the 64 bit (also called x64) one.
There is 0 benefit from having them both installed, and you'll encounter more problems then it may be worth. Actually, you will encounter more problems, and it just isn't worth it.
Also, please only create one (1) thread per problem. You'll make the Admins angry