Do you only have the one ~150Gb hard drive in your PC, or do you have a larger hard drive partitioned?
If you have just a single ~150Gb hard drive, that's small for a hard drive these days and ~£50 will buy you a 1TB drive and ~£70 will buy a 2TB drive and you can use utilities to copy your old files to a new drive so that you don't have to re-install Windows and all your software and it will be a long time before you fill up 1 or 2 TB.