if you are overwriting an existing file, save it as a different name, therefore it isn't "writing to a file", rather it's "making a file".
Format your hard drive if you have a disc to install the OS again and a key. Or defrag it at least every 2-3 weeks. Also CCleaner can remove heaps of old files and make your PC run smoother, when i first used it, it removed 10 GB of bloody potato. It used to be called bloody potato Cleaner
Don't know if this helps, let me know