How to delete unused files under C:\WINDOWS

Leave those Windows files alone. Do NOT delete the $hf_mig$ folder since it is necessary for future updates. You can safely delete the hotfix uninstallation filesONLY . These are the files which begin with $NTUninstall and ONLY those files.

After you do that, get OUT of the Windows directory. If you are scrambling about for a mere 178MB, then you need to uninstall programs you don't use, copy your data (documents, pictures, music, etc.) to an external hard drive and then delete those files from your internal hard drive, or even better - purchase a larger hard drive and clone your current one to it.

You can use CCleaner to safely and effectively remove temporary/Temporary Internet files butONLY THE CLEANING PART OF THIS PROGRAM. DO NOT USE ANY REGISTRY TOOLS .

http://www.elephantboycomputers.com/page2.html#Maintenance
http://www.elephantboycomputers.com/page2.html#Backing_Up

The various .NET Framework entries are not versions of the same program. They are different and are used in programming various applications. If your printer software was created using .NET 2.0 and you remove it, your printer software will stop working. Leave the .NET Framework items alone or some of your programs will stop working and you won't be happy about that.

LEAVE THE $hf_mig FOLDER STRICTLY ALONE OR YOU WILL BREAK WINDOWS. Use CCleaner to remove Temporary Internet Files instead of doing it manually.

Your partitioning scheme is not as useful as you think it is. While it is OK to have a separate partition on the same hard drive for data files (documents, pictures, music, etc.) it is senseless to put program files on a different partition since they will have to be reinstalled anyway if you need to do a clean install of Windows. On desktop computers I prefer just to add a second internal drive for data instead of partitioning a single drive. I very much doubt that putting your page file and temporary files on a separate partition has given you any appreciable speed/efficiency boost. Better to just have enough RAM. You can change your partitioning with third-party partitioning software such as Acronis Disk Director, Easeus, etc.

You forgot to mention how large your hard drive is. If it is under 250GB, I wouldn't bother partitioning it at all. Just back up your data to external hard drives as you are already doing. For the easiest recovery, use an imaging program like Acronis True Image and image your perfectly-working system and save the image(s) on the external drive. TI can do incremental backup imaging so your images are always fresh.