Free up some space on your computer's Hard disk running Windows Vista

I've Windows Vista Home Premium OS on my laptop. I was trying to find some space to copy a big file on any partition on my Laptop's drives when I noticed that C:/ drive is left with almost no space despite being a 25 GB partition and no secondary software (other than default OS software) installed on it. Neither it has any big media file or anything else.
I was wondering what could it be eating all the space on C:/ drive! When I started looking for help at several forums, got some tips, tried and was able to free up around 25% of space on C:/ drive. Here is what I tried and worked for me -

Tip 1 - Use 'Disk Cleanup'. A utility that comes bundled with the Windows. In Vista, click on start, type Disk, select Disk Cleanup from the filtered list and select option to clean for all users.

Tip 2 - Use 'vsp1cln.exe' utility , If you have SP1 installed. Typically You can find it under C:/Windows/System32 folder, or else you can go to Start->Run, type 'vsp1cln.exe'. It will do the rest for you.

Tip 3 - Disable Hibernate option, using the Disk Cleanup utility. It might free up at least 1 GB of space.

Tip 4 - Regularly cleanup the 'Temporary Internet Files' and 'Cache and Cookies' in your browser. (Tools->Internet options)