Sounds like you're talking about you're hard drive, not your memory. If I were you I'd pick up an external drive and move your files over. Then you can install anything new from there as well. As a rule of thumb, once "fill up" half of the space on your hard drive then things will start to slow down.
Also dell makes very good laptops, while hp ones tend to overheat.
Generally you can find a nice external drive for under $100
You're looking at hard drive space, not memory. Both memory (RAM) and hard drive are upgradable. A new 500GB drive will be something like this: [link] If you're not afraid to get your hands dirty, you can install it yourself. You'll also have to install your OS on it.
Hm! Thank you for the guide and the link to the bit on Amazon!
I'm not sure I could take things apart like the guide shows. I'm the sort that any small pieces are bound to get lost or something. So would I be able to buy the drive and take the laptop and drive somewhere?
I'm sorry but it is really hard to tell what you mean by 255 without giving it some units. if its 255GB then that's an insane amount of memory, if its 255MB then you need and upgrade and if its 255KB then why are you using a 20 year old pc.
I have my doubts that 255 is the amount of ram due to the way that 255GB is huge and 255MB is not enough to run win7 is it possible that that is your hard drive that is 255GB (with 60GB remaining)
At the moment new ram costs about £20-25 for 4GB which is fine for most things
i would need to know what model laptop it is in order to give advise on self fitting bu a google search of 'replacing ram for <insert laptop name here>' should give you the information you need