This is a short version of my post-own speed/Clean guide. I'll post the complete one when i'm not afraid of falling asleep on my desktop :-D.
First of all, Download RegCleaner. When you have installed it, just leave it be we'll get back to that later.
Defragment your PC and run Disk Cleaning. Instructions on how to do that is listed on the bottom of this topic. It can take several hours to finish this.
Once you are done, open RegCleaner, and read the instructions that is listed above each tab. A tab is like the little blue box saying Startup List.
In the Software list, you should delete all things there you know you've HAD but don't have ANYMORE! The startup list should be as SHORT as possible. I only have MSN, Daemons tray and my desktop in the startup list. And AVG.
The uninstall menu is just a shorter, quicker way to remove your files than doing it from the right click + delete or the removal list somewhere.. Its more efficient, cause it deletes all the registers attached to it.
The file tab is the tab you'll spend hours on. If you haven't cleaned your PC in a long long time, you'll probably see half a million N/A Files. Delete all those (but before you start doing that, be sure to read at the bottom on the topic!)
The New file tab is a list which you can right click and create, e.g a .txt file. I keep it very short. You should delete all unnecessary things like, creating a photoshop picture.
The shell extension, is well honestly i have no idea. I'll write on the bottom of the page on how to clean that with being as clueless as me.
The backup list is handy. If you deleted something that have an obvious side-effect you should restore it from the backup list. If everything is running nice for a week, just delete everything there.
The bottom page
How to defrag your PC
First of all you click "My Computer" from the 'start' list. The windows button in your desktop toolbar, or on your desktop window.
Right click your primary disk (most likely C and click the tools tab. Click Defragment and then click Start Defragging again. You could wait for several hours, depending on the size of that station. If you have many huge ones, several terrabytes of space, you could wait for days!
Run automatic Disk Clean
Go to My Computer and right click your primary disk, and click "Disk Clean". You should wait a few moments untill it pops up a list. Tick (√) all the Tickable text and click OK. IF you delete your cookies often, this shouldnt take so long. If you didn't delete your cookies in 3 years, then expect to wait as long as the defrag.
Automatic Registry Cleaner
If you are terribly lazy, and dont want to manually, safe and secure, and make sure you got all the dirt in your registry, you could do a quick way.
Start Reg Cleaner and Click Tools at the top, and then Registry Cleanup and then "Do them all". You'll have to wait 10 minutes.
Scan your PC
Scan your PC with an Anti-Virus. I use AVG 8.5 Security Pack ('Pro' version)
If you do not want to pay, you should try the 'ultimate' combination of the Lavasoft Ad-Aware and a free-version of AVG.
My notes
On my old laptop, i could barely run Gothic 3.
I did this + a little extra that i will mention in my full guide. Now i can run it on max resolution, and medium/high graphics. I could also run Crysis on low :P.
Enjoy! Any suggestions are welcome, and other moderators, feel free to clean my messy post xD.
Best regards
~InFeCtoR