Helping people with computers... one answer at a time.
As machines get older and older the latest software upgrades demand more and more. There are ways to maximize an older computers abilities.
I Gave my son a 1 gigahertz Compaq laptop with XP home and 256 megabytes of ram. He only uses it on line, via a cable connection, and as you can imagine, it's slow. You can only upgrade ram to a max of 384meg. Will that be fast enough or can I configure something else to improve performance>
Ultimately it depends on what you mean by "uses it on line". If that simply means downloading email, chatting and viewing web pages, it seems like that machine should be fine. Bare minimum, perhaps, and adding the RAM certainly won't hurt.
If on-line means viewing videos or playing on-line games or other types of similar activities, other considerations come into play.
First, let's be clear, for most people the speed of your internet connection is the slowest part of your whole internet experience. It doesn't matter if you have a low-end or high-end machine, most of the time web pages display slowly because they download slowly.
And it may not be your connection. You may have a fast connection (cable, for example, is capable of something like 8 megabits per second, or faster), but it may be throttled for any number of reasons. Cable in particular is notorious for this since you're actually sharing your internet connection with some group of neighbors. I recently heard from a friend who was getting near dial-up speeds from his cable connection at times because his "node", or cable network, that he and his neighbors were on was saturated by everyone attempting to use it at the same time.
So step one: check your internet connection, make sure it's living up to your expectations.
Step two: update and scan. By that I mean follow the steps outlined in Internet Safety: How do I keep my computer safe on the internet? to keep your machine up to date and free of viruses, spyware and other malware. Particularly on a lower-end machine a malware infection can definitely result in performance problems.
Step three: tame startup. This can be a little bit of work, but there's typically a lot of unnecessary software that starts automatically when you sign in to Windows. While it's difficult for me to answer "do I need this" for each possible startup entry (the answer depends on your machine and what you do with it), this article discusses the concept and links to a couple of tools: What's all this stuff running after I boot Windows?
Step four: tame services. With a little more research you can turn off even more software by looking at the Windows Services - components of Windows that run in the background - that you may not need. Once again knowing which you can and cannot turn off depends on your situation, but this article What Windows Services can I turn off? is a great start and includes pointers to some reference sources. The most popular such source might well be Black Viper's list of XP Services where he does include recommendations for each.
After checking your internet speed, all of the above is about reducing the "other" software on your machine so that it has more available resources to do what it is you need: "use it on line", whatever that might mean to you.
There's another approach that I'll mention as well: Linux.
The very popular Ubuntu distribution calls out 256 megabytes in their system requirements, so I can't say for sure how well it'll run. My guess is it'll run just fine, as I tend to trust their system requirements as being more realistic than those specified for Windows.
But depending on your own expertise and interest in getting a little geeky, there are several other distributions out there that are specifically designed to run very well on minimal hardware. They might be worth looking into. ("Puppy Linux" comes to mind, but I'm sure there are others.)
In many cases (including both Ubuntu and Puppy) you can boot from a "live CD" and try it out before installing to your own hard disk.
And finally, no matter which rout you go, adding that extra 128 megabytes of RAM certainly won't hurt. I can't guarantee that it'll help, but these days it's an inexpensive addition.