Its too old I'm afraid. Sorry.
You could make it a bit faster by adding more memory that always makes things quite a bit quicker but the newest games require a faster processor than you have. Perhaps you could upgrade it but even if you could its unlikely to make a huge difference.
If you're generally happy with it and just want to boost it a bit then add more memory. Failing that its a new PC I'm afraid. It needn't cost a fortune though, if you use your existing monitor you could get something like this click here add for Windows XP and if you want to play games add another £100 for a graphics card and there you go. Theres others as well if you have the money.