First off, Windows 7 64 bit requires 2GB of RAM.
Quote: Originally Posted by http://windows.microsoft.com/systemrequirements
If you want to run Windows 7 on your PC, here's what it takes:
1 gigahertz (GHz) or faster 32-bit (x86) or 64-bit (x64) processor
1 gigabyte (GB) RAM (32-bit) or 2 GB RAM (64-bit)
16 GB available hard disk space (32-bit) or 20 GB (64-bit)
DirectX 9 graphics device with WDDM 1.0 or higher driver
So, right there your system doesn't meet the minimums to install a Windows 7 64 bit operating system. If you want 7, you must use a 32 bit version. You can go ahead and be pissed off now.
I don't see any Windows 7 (or Vista) drivers
available from HP for your computer. That would indicate that Windows 7 may not work, or if it does work it may take a lot of work from you getting it to work. There won't be any support from HP, so you'll have to do a lot of research on the particular hardware you have to find Windows 7 drivers.
Are you trying to dual boot XP and 7?
Why can't you get another disc? You can download Windows 7 from Digital River and other sources - completely legit copies of Windows 7 x64 and x86, both with and without SP1. You can use your existing Windows 7 Ultimate key and it will work just fine.