Windows has a search capability (it should be on the Start menu).
If you say you want to search for "files and folders" you can specify certain parameters (date time etc).
One of the parameters is file size. Specify a large file size, then if you find nothing make the size smaller and search again.
Keep searching till you find the largest files on your PC.
You may find it is video files (they are often the largest).
If you want to keep them put them on to CD or DVD.
If you dont want them then delete them.
Deleting one video file will probably save more space than uninstalling 20 programs.
Note that if your search finds a file and you dont know what it is DONT just delete it, it may be an important file that Windows uses. Only delete personal files that you know what they are.