I work with databases and am not an actual IT guy, but I can get you started.
couple of questions for you. how much drive space is free? how much physical memory do you have? what's your O/S, i.e. which version of windows are you running? ok. three questions then. the reasons I ask are:
- you need at least 10% of your hd free or your system will slow considerably
- with less memory on your system (<128-256MB), swap files become larger and more necessary, and that means you need more free space on your hd. it's about headroom.
if you're running win xp on a laptop, you probably have hibernation enabled. you can free a little space - 256 MB or so - by turning it off: start | control panel | power options | hibernate, then uncheck the "enable" box. having hibernation enabled reserves drive space in order to save the current state / instance to disk, and disabling this feature simply releases the drive space necessary to do that.
remember if you choose to get a bigger drive you'll be replacing the hd in your laptop, not adding another one, so you'll want to think about the consequences, like reloading your O/S and all your programs and transferring all your data. this is not easily done without another computer, a network and another computer, or external storage.
my best advice is to consider how much hd you're using for programs and how much for data, and make a decision whether it's best to get a bigger hd or to uninstall little used programs and delete some data.
couple of other things if you decide to try to clean things up a bit... you'd be surprised how large media files have become these days - video is huge, audio can be huge, pictures can be large, etc, and none of these files compress very well - so data can take more space than you might think. take a look for yourself. also, take a look at cleaning up your mailboxes (sent and deleted items folders) and your temp files, and don't forget your internet explorer cache, etc.