Free up disk space
By freeing disk space, you can improve the performance of your computer.
1-Delete any unnecessary programs
2-Empty the Recycle Bin
3-Delete Temporary Internet Files.
4-Use the Disk Cleanup :
Click Start, point to All Programs, point to Accessories, point to System Tools, and then click Disk Cleanup. If several drives are available, you might be prompted to specify which drive you want to clean.
Clean Your PC from Spyware and Adware
These are harmful programs that download themselves to your computer to collect information about you or to show you some advertisements, and it can really slow your PC and annoy you. Use a program to remove Spyware from your computer. A great software that can perform this is: NoAdware.
Read more : What is Adware?
Defrag your hard drive
Use Disk Defragmenter (use it monthly and when you add alot of files to your hard drive):
Click Start, point to All Programs, point to Accessories, point to System Tools, and then click Disk Defragmenter.
Analyze after it finishes, click Defragment.
Detect and repair errors:To run the Error Checking utility:
2.Click Start, and then click My Computer.
3.In the My Computer window, right-click the hard disk you want to search for bad sectors, and then click Properties.
4.In the Properties dialog box, click the Tools tab.
5.Click the Check Now button.
6.In the Check Disk dialog box, select the Scan for and attempt recovery of bad sectors check box, and then click Start.
7.If bad sectors are found, choose to fix them.
Adjust the visual effets :
From your control panel choose System > Advanced > Performance > Settings > Visuals Effects, choose the options that suits you. If you want maximum performance choose Adjust for best performance, Later if you feel that windows is missing some flare yo can go and change it as you like it by choosin custom.
If your computer is still suffering from slow windows boot or slow performance after doing all the above, read this post about fixing errors in your registry which can really help to make your computer faster and more stable.
I hope that helped.