If you wish your Linux Mint MATE desktop to look like the Windows XP operating system from Redmond WA, then you only need to install these two themes into your ~/.themes folder and then select the XP Luna theme in the Preferences->Appearance window. I have my MATE desktop setup with the two panels in the traditional Gnome manner with the Mint menu and this looks awesome. Give this a try if you want a XP lookalike Linux desktop.
XP Luna GTK theme for Gnome and MATE.
XP Royale GTK theme for Gnome and MATE.
This is a very highly rated theme that has just been updated. The Adwaita Cupertino theme for Unity and Gnome Shell.
Another way to get some good themes for your Linux Mint MATE desktop is to run this command in a terminal.
sudo apt-get install legacyhuman-theme shiki-colors faenza-icon-theme
This will install a legacy Ubuntu lookalike theme for your Linux Mint system. And some other cool themes as well.
And this command will install some awesome GTK theme engines for you to play with. The Cleanice themes are pretty good.
sudo apt-get install gtk2-engines-cleanice gtk2-engines-wonderland