If you want to make Windows 10 look more like Ubuntu then check out Maverick, a Windows 10 visual style inspired by the Ubuntu Ambiance theme.
Upgrading from Windows XP to Lubuntu? This XP-style theme should make the switch easier, resembling Microsoft's aged OS in almost every area.
WINE and/or Windows XP users wanting to add some Ubuntu style to their desktops have long been able to do so by using a custom-made 'Ubuntu Theme for Windows'. That theme has been updated to resemble Ambiance (and Radiance) as found in Ubuntu 12.10, having previously been modelled on Ubuntu 10.10.
Dual booters, or even full-time Windows users, who want to add some Ambiance style to their Windows 7 desktop can do so by downloading and install the 'Ubuntu 11' theme for Windows 7.
As a hostage of ancient hardware I'm forced to keep a copy of Windows XP close to hand. If there's one thing I hate more than the need to run virtualization software at all it's the lack of harmony it creates in my daily workflow. That's why I use an Ambiance theme for Windows XP.