First you must make sure you have some type of recovery before proceeding. It's your PC and I am not responsible. I highly recommend creating a restore image anyway whatever you use Right Now. Back it up every so often when you know that you do not have any viruses or anything.
I personally use Acronis True Image Home but it does cost. I create Images on a separate drive where I can reach them easily with an Acronis boot CD. There is Macrium Reflect which is free but I haven't used much and don't know how to reach that in case of failure.
or
Win 7 has a built in Recovery which works also.
You will need a separate Hard drive/USB big enough. You can write these to Dvd but it will take 4 or more depends how big your system is.
Read this and get real familiar with it.
http://windows7forums.com/tweaks-guides-howto/46010-windows-7-comes-lot-repair-options.html Advantage to this is you will be able to reach this by Tapping F8 when system is booting and choose Repair your Computer Select this Hit enter, Select keyboard, Select User and enter Password and proceed to screen with list
Choose Windows Complete PC restore. There will allow you to select the backup and restore it.
To make a System Image in Windows 7
Type sdclt in the search box on the Start menu. Upper left select the 'Create a system image', let it find a drive/usb with enough space.
Choose Next. Choose Start Backup. On Mine it creates a WindowsImageBackup folder that is 15.8 GB backup of my system drive C: currently at 25.4 GB
All About Resource Hacker in a Brief Tutorial - Tweaking with Vishal Copy the dll's to another folder elsewhere and add your images. You can extract these images out of the dll to same folder so it will give you size. EX: 1024x768
These files need to be exact same size as they are in the dll.
spwizimg.dll change 517.bmp and 518.bmp
imageres.dll change 5031.jpg to 5043.jpg
There are more to change but that will get you started.
I have been wanting to write a complete tutorial on all the things you can change for awhile but haven't had time.
There are programs out there also but I prefer doing things on my own