What OS are you using? I have an old laptop with similar specs to yours, I formatted the drive and installed Bodhi (a lightwight OS), Xubuntu and Lubuntu are also good OS for older machines. Win 7 may work with ready boost but I tried with my laptop and it wasnt that great. The best option though is suggested by Fabio2011, more RAM is the best thing you can do with it, you may struggle to get an SSD to fit into the laptop depending on what connection the HDD bay uses.