Going off of what other people have said:
http://www.piriform.com/ccleaner Ccleaner is an awesome program. There are options to have this run every time your computers starts (which may add to your start up time but your overall processing in general will benefit.) Keep in mind that you may want to add cookie exceptions for sites you use regularly (gtplanet.net would be one!). Before you download tho, go to the downloads page and scroll to the bottom and there is a link for the builds page. At the bottom of that page there is Ccleaner Lite which has some of the garbage they include (tool bars, etc) left out.
http://www.piriform.com/defraggler This is useful for Xp (which you have) but less useful for Vista and Win 7. This program also has a "Lite" version under the builds page. This you can also schedule to run whenever you want. It also has a "quick" defrag option which is useful when you don't want to wait for a full one.
Adding RAM to your laptop is probably the cheapest way to get a noticeable difference in performance. Most laptops have made it relatively easy to install new RAM by including a removable panel on the back which provides easy access to the expansion slot. This is MOST laptops. I had to just about take mine apart entirely. This is something you'll want to look into BEFORE you buy the RAM if you're not comfortable taking your laptop apart.
A couple "soft" changes that you can make to your system to increase performance: Use msconfig to disable useless startup objects. To do this, Press the Windows key + R, or under the start menu there is a Run... box. In this box type "msconfig" without the quotes and press enter. This will open up the "System Configuration Utility." There is a tab "Start Up." Generally speaking I disable everything listed under here except for the antivirus. But that's up to you.
Next, you're going to want to get into your system properties. Easiest way to get there is to right click where it says "My Computer" and go to properties. Under here go to the "Advanced" tab and click Settings under the "Performance" section. The first tab that pops up, select "Adjust for Best Performance." This will make everything look grey and flat, but it will definitely make your computer perform better. Next go to the Advanced tab under this section. At the bottom where it says "Virtual Memory" click change. Here you're going to want to make sure "Custom Size" is selected. (If windows manages this then it constantly grows and shrinks the page file, which actually takes resources, slowing your computer down.) The amount for Initial and Maximum should be identical (so your computer doesn't have to worry about resizing it). The amount should be ~x2.5 your computers Physical RAM. That means if your computer has 1gig of RAM then you should but 2048 in both. Oh! on that note. You're going to want to use 1gig = 1024 for this estimate. If you have 512 megs of ram you'll want 1280 in both boxes. 2 gigs = 5120 and so on.
Next a couple of system utilities. In the "Run" box (windows + r), type "cleanmgr.exe" without the quotes. This cleans alot of the same things that ccleaner does but it has a couple options that ccleaner does not. Clean everything.
Make sure that you're computer is completely up to date with it's windows updates. When you go to windows update, select "Custom" and not express. This will often show you some hardware options (drivers, etc) that aren't shown in the Express windows. Updated drivers = good.
A couple last suggestions. Stop using internet explorer (if you're still using it). There are so many things wrong with IE and they seem to just keep adding more (ever notice that when you click the stop button in IE it just keeps going, or if it does try to stop it LOADS another page? why not just STOP when I tell you to!?!? LOL). I suggest firefox (
http://www.mozilla.com/en-US/firefox/) but alot of people like Chrome (
http://www.google.com/chrome) but I'm not a fan.
Make sure that you're computer has an Antivirus. AVG offers a free one if you dont want to pay for one (and yes people say that antiviruses use system resources but rest assured that a VIRUS will use more resources, oh and then steal your credit card number
).
http://free.avg.com
Another program is called Malwarebytes. This isn't a "anti-virus" it's an anti-malware. Two similar but different things. It's also free.
http://www.malwarebytes.org.
Alright, that's all that I can think of off the top of my head. Hope I didn't overload you. If you have any questions feel free to ask.
But I'll take it step by step until Im through it all. Also, I have Google Chrome so could I delete Internet Explorer as its only taking up space. 
