The problem here is support. Browsers themselves are dropping Vista and XP along with a long list of Anti Viruses, even Youtube under Windows 7 and above will struggle.
AMD Turion™ 64 X2 Dual-Core TL-64 2.2 GHz
3GB PC5300 DDR2 SDRAM. Maximum capacity 4GB
Radeon HD2400
Light weight Linux distros will give him the support and drivers to make just about anything run and use far less resources.