The advantage of partitioning your hard drive is the ability to separate the operating system from your data and personal files. A separate partition for the OS allows for an easier annual reinstallation of Windows as well as a possible safeguard in case something should happen to the operating system such as a virus. The advantages become clear when it comes time to defragment the operating system and all is finished within a 20-25GB partition. I could not imagine having to wait for all the rest of the 225GB drive, with thousands of large files that do not need defragmentation, to finish.
To Place Windows System Folders, That Contain Personal Data, On Another Partition
1) After installing the OS on a 20GB partition, then create a hidden "D:\System\" folder on the second partition. Make sure only that first "D:\System\" is hidden and not the folders soon to be within it.
2) Create "D:\System\Desktop\" and "D:\System\My Documents\".
3) Select Start, right click on "My Documents", select Properties, and change the target folder to "D:\System\My Documents\". Select the option to move all files to that location.
4) Now is the tricky part but it is easy so do not worry. Open the Registry Editor with Start, Run, type in "regedit", and select the OK button.
5) Make a backup copy of the registry.
6) Select Edit from the top Menu bar and Find (CTRL-F). Type or paste in "D:\System\My Documents". Ensure Keys, Values, and Data checkboxes are checked and then select the Find Next button. Everywhere you find your new location for the My Documents folder, look for the Desktop variable. Then manually change the Desktop variable to your new location at "D:\System\Desktop\".
7) Do this for each user on the system individually by logging out from other users and logging into each user.
Now you have your personal files from the Desktop and My Documents folder in a safe place in case something ever happens to the operating system files, such as a virus. It is easy to believe the freshly built system will last forever but experience tells us all that something will eventually happen to the system, requiring a rebuild and possible lost files and configuration settings.
Keys that will get changed are:
My Computer\HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\ Explorer\Shell Folders
My Computer\HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\ Explorer\User Shell Folders
My Computer\HKEY_USERS\...random numbers...\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders
My Computer\HKEY_USERS\...random numbers...\Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders
Always make a backup copy of the registry before making any changes to it.