If you have use any special hardware drivers that don't come from Microsoft, they won't work, and you will be deprived of that hardware. For instance, last I knew, Intel's ethernet boards, which are in fairly widespread usage, cannot be made to work with 64 bit Windows XP. I guess Intel is not eager to help a version of Windows that only runs on AMD chips.
The main advantage of 64 bits is the support for larger memory, but unless you already have 4 GBytes of RAM, and are itching to add more, this won't matter in the slightest to you. Most of us have a half GByte (also known as 512 MBytes) or one GByte of RAM (well, DRAM, to be precise), and don't need this. Folks running large corporate databases and big number crunching scientific computing jobs are more likely to need this much memory. From what you say, I am quite certain that you do not have, and have no need for, this much memory. So the one serious advantage of 64 bit Windows is utterly useless to you.
If you do change to the 64 bit version, I understand that Microsoft will disable the product key you have to license your 32 bit version of Windows XP. You will have to buy another copy of Windows XP ($100 or $200, at least) if you decide to go back to the normal 32 bit Windows XP. If you have support from your computer vendor for Windows XP, this will likely be voided by applying the 64 bit version to your system.
If you play games on your system (or you have a teenager who does) you want to avoid the 64 bit Windows like the plague. Graphics card drivers are not up to speed, and this can result in catastrophic loss of gaming performance. Applications that are recompiled for 64 bit code can, in some cases, gain a few percent of performance, if their data access pattern is favorable. Unless you perform carefully controlled benchmarks, you will never notice this minor gain, if it even applies to your usage pattern.
Even Microsoft discourages most users from this change. From their own website http://www.microsoft.com/windowsxp/64bit/upgrade/default.mspx :
In short, to answer your initial question, I recommend that you do not do this.Before you make the decision to move to 64-bit, we recommend taking the following steps:
• Read the information on this Web site about Windows XP Professional x64 Edition. Unless you are pushing the boundaries of the 32-bit architecture, you will probably find that a 32-bit operating system is still the best option.
• Investigate whether or not 64-bit device drivers are available for the components in your PC and the peripherals that you use (scanners, cameras, and so on). Since your 32-bit drivers will not work on this version of Windows, it is important that you make sure your devices are supported. You can find many of these supported devices on Windows Marketplace.
• Back up your data and settings. Windows XP Professional x64 Edition requires a "clean installation," meaning the contents of your hard drive will be erased during the installation.
This is the information I need. I read the information you posted but still could not decide.
Thank you.