degunking my Mac

In HardDrive/Library/Application Support/ I found a GarageBand folder with 1.8GB! Even though I previously deleted GarageBand, because I have no need for it right now, I had no idea that there are Gigabytes of unnecessary junk on my hard drive. HardDrive/Library/Desktop Pictures is another 33MB! It really makes sense to do a clean install once in a while, then get rid of useless language and code files. A week ago my hard drive was filled with nearly 30GB, now I am at less than 10GB with no important documents missing! Now all my Mac stuff should fit on one double layer DVD+/-R or DVD-RAM!