Emmie, find the little local man who is an independent - should cost you around 30 squid. Ask him to do a clean-up. If you are using Windows, your machine, which doesn't have oodles of memory capacity to begin with, may well be clogged up with past Windows updates...they don't remove old ones when updating.
On my last machine, I had 44GB used out of 80. I bought my new one, an Asus, from my man and he transferred the files over - to my amazement it was 21GB out of 280 - he explaining that over half my memory on the old machine was these back-updates..... Your speed will seriously improve....