That one is ancient but should run Win 7 x86 just fine, don't install x64 on it. Your "test" system is not really representative compared to hers, your has UEFI onboard and hers never even heard of it.
So, would it be worse if she had the 64-bit version? She told me that the 64-bit version would work much better for her since her CPU is 64-bit... anyway, I'll tell her about this. Thank you very much for your reply.
I was me definitely the one to trying to help her xD She doesn't have much idea about PCs and well, I do, a little bit. I know how to do OS installs but I didn't understand this error and that's why I was looking for help. Yeah I know but she simply asked me for help as she currently on her 32 bit OS plays some games and they run well, not entirely bad but they could run better. And of course, to play a game she wanted to, she needs a 64 bit W7 and asked me to help her with this, she also said that maybe other programs and games would run better with a 64 bit OS.
The architectures (32bit/64bit) a CPU is capable of only refers to its instruction sets. It does not say anything about the power of the CPU. With an old CPU and only 3GB RAM, Windows 7 64bit will most probably run slower as 32bit, as 64bit needs much more RAM to run without happy-trashing away on the page file. You need more than 4GB of RAM to really run 64bit Windows conveniently. Below 4GB, it's basically molasses flowing uphill.
What does it matter, that is only a test, the real target system is from the vista era, no UEFI present.
The very over...over....oversized screen shown at the OP is not taken from the system on which the client wants win 7 ultimate x64 to be installed. ps, it runs win 7 x86 at the moment, that means no UEFI.