Here's a small list of things you can do to speed up your computer, most of it is quite simple, I might add some more things over time.
Check the hard disk for errors (Source)
If you're using Windows XP, you can use the Error-checking tool to check the integrity of your hard disk, including file system errors and bad sectors.
To run the Error-checking tool:
1. Click Start, click My Computer, and then right-click the local disk that you want to check (usually, this is drive C).
2. Click Properties, and then click Tools.
3. Under 'Error-checking', click 'Check Now'…. Make sure both check boxes are selected, then click Start.
Delete unused programs
Doing this frees up space on your hard disk.
To delete unused programs:
1. Click Start, click Settings, and click Control Panel.
2. Click Add or Remove Programs.
3. Scroll through the list and look for applications you don't use, then click 'Remove' and follow the simple UninstallWizard that comes up.
Defragment your hard disk
If you're using Windows XP, you can use the defragmentation tool to optimize disk space.
To run the defragmentation tool:
1. Click Start, click My Computer, and then right-click the local disk that you want to check (usually, this is drive C).
2. Click Properties, and then click Tools.
3. Under Defragmentation click Defragment now and then Defragment.
(When defragmenting it's best to leave the computer until it has finished, depending on the state of your hard disk this can take many hours).
Disable unnecessary startup applications
This can be done to stop unwanted applications from automatically loading after logging on to your pc.
To do this:
1. Click Start, click Run, and then type 'Msconfig' and press Okay.
2. In the window that pops up, click the Startup tab.
3. Now simply untick the box for applications you do not need.
(A useful way of seeing which applications are not needed, is to look at their Location. If they are from 'My Documents', 'Desktop' or anything similar, it's likely that they are junk programs; however this is not true in all cases).
Creating a Run Command shortcut
Doing this can make it quicker and easier to open folders that are tucked away deep within your hard drive.
To do this:
1. Locate the folder you wish to create a shortcut to, right click and Copy it.
2. Go to C:\Windows, right click and select Paste.
3. Rename the folder that has now been pasted in to C:\Windows, so that it has no spaces in it.
4. Now whenever you want to open this folder, press Windows Key + R (or click Start>Run) and simply type in the name of this folder and press OK.
Prevent pop-ups and security threats
Download the free program, Windows® Defender (Beta 2) from Microsoft.
Remove malware (malicious software)
Download the free program, Microsoft® Windows® Malicious Software Removal Tool from Microsoft.