Windows 7 - How to delete unwanted/unknown programs and such

I have a 64 bit laptop
When I go to 'my computer' and OS appears under Hard Disk Drives, it says I have 25.3 GB free of 283 GB. I deleted a lot of images and folders and programs that I didn't need, I even deleted over 5,000 songs I've had but it's made no difference. I've gone through all the folders that I know of and into Uninstall and gotten rid of what I could.
The bar is red and there is not much room left. How can I find things to delete to make this go down? It never used to be like this and I think it's messing with the performance majorly.

Have a look .... it will help you to a great extent

Hard Disk Space - Free Up and Recover

Have you been using your internal hard drive for backups?

If so, you'd do better to invest in an external hard drive and backup to that, and then you can remove any backups on your internal HDD.

The link that Arc posted should help too.

Ultimately, you could always replace your internal HDD with a bigger one.

WinDirStat gives a good graphical indication of where your storage is going. WinDirStat - Windows Directory Statistics