You cant go from XP to 7 without upgrading to vista in the middle or doing a clean install. I also dont believe that you can go to 64 bit from 32 bit without a clean install. Your system should have no problem with a clean install if you can do one, if you had to burn your own disk do it at the lowest speed possible to reduce errors.
Please note that when migrating from Windows XP to Windows 7 you will not have an "in place upgrade" option. You will however have the option to select "custom" install when prompted. The Windows 7 install process will then copy all of your data in "My Documents" over to a Windows.old folder within Windows 7 itself. All applications and documents stored in other locations will have to be reinstalled / transferred manually.
For more information on the Windows 7 Upgrade, please go here: http://bit.ly/3DvynK
For additional assistance with the migration of Windows XP to Windows 7, please go here: http://tinyurl.com/mhbep4