You should not delete it by going to C Drive via My computer but instead goto control panel -add/remove programs and remove those programs which you no longer use. After removing those programs still some files will remain in c:\program files\. You may delete these files.
There are many hidden files and important files in C: if you delete any boot record or "ntuser" files you will end up in deep trouble. Your OS Will be corrupt. You will have to re-install the operating system.
Apart from that there will be huge memory dumps, use Ccleaner, which is a crap cleaner helps you clean the system safely. You can download it its a handy tool.
You might have stored some songs and videos in c:\ , i would advise you to move it to a drive that is less used. Eventhough you see 2 GB or more free space in C: if other drives are not free or do not have free space then your C:\ will be explicitly used by the Operating system for creating a Virual Memory.
For those who do not understand what isvirtual memory: The virtual memory is temperory memory created by operating system on slower disk(HDD), Why we need? Electronic memory(RAM) is costly and Volatile,the reliability of storing the data is less. Therefore for storing the data for longer time period safely we need hard disk.
When programs bigger than the RAM(Main memory) has to be executed by the processor It is required for the processor to access the Bigger program in some way in order to execute, therefore the bigger program is stored in temperory workspace(Virtual memory)Created by the operating system and how to access this space is stored in the RAM. Along with the essential processes(Modules) of the bigger program to be executed. they get executed in a scheduled fashion.(Mostly Round robin Scheduling is done)
Therefore in order to have Virtual memory space in your system its better to isolate your music and video in any removable drive,(External hard disk or pen drives, CDS)
Once you are done these three you wont face this problem
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