It is possible to install windows Vista on Sony Playstation Portable (PSP), how you can do this is expalin in this guide which give you a detail step by step procedure for donig the same. You can install Window Vista on to PSP for better navigation and use of it.
Requirements:
Steps for Installing Windows Vista on PSP:
Step 1: Insert the Window Vista Installation Disk into your PC.
Step 2: Click on My Computer icon, and than open your CD or DVD drive
Step 3: Now insert the blank universal media disk into its reader.writer which is connected to your PC.
Step 4: Now Copy all the files of Window Vista on to the Universal Media Disc.
Step 5: Insert the Universal Media Disc which now have all the files of Window Vista into your Playstation Portable (PSP).
Step 6: Boot your PSP and follow the installation instructions which is similar that you follow while installing it onto PC.