Warning , these are mere advices , and before installing this on your windows xp os , please backup all yours drive with acronis true image or through following process described by gizmo:
and also do it on your own risk as these are third party softwares and do it on your own risk and always prepared for the worst so that nothing worst will come in the process .
Before starting this , just make sure that you have a bit of spa re ram so that windows vista GUI would be runing appropriately and smoothly.
Vista Transformation Pack 7
Start menu, the Control Panel, system dialogs, icons, Vista style, transparency function. Just be care ful as I have faced difficulties during unistallation but others says it is a smooth sailing and please refer the forums for much details and also googling it and make one small research on it before instlling on it windows xp.
It modifies about 400 of your system files. Customizability feature of this should be apprecia ted by yours. It will keep backup of all the changes , which should be a sweet for you whenever you need you can revert back to your original feature of windows xp as far as I realise it wont destabilise the system but it still needs a careful system instalaltion.
Windows Blind Gallery: http://www.wincustomize.com/Skins.aspx?LibID=1
It claims to be memory friendly , so it would not slow down or hang your system , It comes with both free and paid versions and free version lacks some features , most of the jobs and necessities of yours can be completed on the free version .