Many users may have encountered the problem that when you open the "My Computer--Explorer" in Vista or Windows 7 environment, Drive C shows a red bar (low disk space), while Drive F shows a blue bar, just as the following screenshot descriptive of the case:
In fact, the main reason about the low disk space problem is that Drive C is almost fully occupied by large number of files with very little free space. For example, this Drive C has only 604MB free space, which shows a warning red bar. However, Drive F has 26.1GB free space, which shows a normal blue bar. So what we should do is moving more free space into Drive C in order to resolve the low disk space throughly.
In Drive C there are many unfamiliar or unknown programs or files (PC garbage) which directly result to the fact that some application programs never execute. The problem is that you can hardly know which programs or files should be deleted. If possible, you can choose to re-install the system and create a larger volume Drive C when you do the partition allocation process. For example, you can allocate 200GB to Drive C, which makes it not easy to be filled up by data. But there are some limitations of this method, you need to re-install the system, waste a lot of time and the data in the hard drive will be deleted.
The second method is that you can use a Garbage Remover to scan useless files from Drive C and delete all of them for the purpose of releasing more free space to Drive C. For instance, hiberfil.sys, pagefile.sys, temporary files of application programs (in Windows\temp menu) and temporary files created by Browser like IE, Firefox, etc. This method has one limitation that you can't resolve the problem throughly because after some time of operation, your PC will create more garbage which make the Drive C showing red bar again.
From the above two methods, we know that they both has some limitations and can't resolve your low disk space problem as you expected because you can't extend/expand the partition directly. How to make Drive C larger volume? You can use a professional tool Partition Assistant - FREEWARE (It's partition manager) to do such kind of work. You can resize your Drive C as you wish. You can move free space from other partition (like Drive F) into Drive C, which keeps your system partition more healthy. For instance, you can increase your Drive C from 8.67GB into 16GB very easily and promptly. This method avoids troubles of re-installing your system and saves your lots of time. You may refer to the article "How to Extend System Partition" for more details. Not only you can easily work out the problem about low disk space, but also you really can benefit from the Partition Assistant. Here is a screenshot: