Hi there rohith1210,
How much free space you've got? We need to know if we are talking about several gigs let's say, or way more.
I think that it would be nice to start with using some disk analyzing tool, that can show you what is filling up the free storage space. There's one in the link that Qhuasar has already provided.
Apart from that, you can:
- Clean temp files.
- Delete previous restore points.
- Run some antivirus/malware scans.
Let us know how this goes,
D_Know_WD