How much free space does it have and what size drive is it? Does it have another Partition? You could buy a larger disk and clone your system on to it. In My Computer, click the Tools menu then on Folder Options then click the View tab and tick "Show hidden files and folders" then untick "Hide protected system files and folders", click Apply and OK.
Then, go into c:\ windows and delete all the files in blue which statr with a $ symbol. They are only folders that once contained Windows Updates you no longer need to keep. Then scroll down to the Software Distribution folder and to Download. Empty that folder.
Look in Control Panel>Power options and make sure Hibernation is turned off then in System, adjust the size of...