Windows 7 Ultimate x64 "Not Responding" Problems

The Exact Problem:
Well you see, I don't know what the exact problem is but it's causing every program I open to not respond.
It's weird though because sometimes when I open a program, it actually runs for like a minute. Then it doesn't respond.

Example Scenario:
When I'm logged in, I open Skype. Skype will work for like 5 minutes, then not respond. And it will never fix itself unless I restart my computer which I constantly have to do...And it's not just Skype, it's every program I open including "My Computer", etc.

As every program freezes, eventually Windows Explorer will stop working and when I click "Shut down" or "Log off", it doesn't freeze, but it stays stuck at the "Logging Off..." screen and doesn't even turn off. So I have no choice but to hold the off button...

*I did not download anything to cause any viruses nor did I touch any settings in the Bios, etc. This happened randomly out of nowhere*

What I have attempted so far:
-disk check
-updated everything (drives, etc.)
-disk defrag
-virus scan
-scan through command prompt

I would re-install Windows 7, but I don't have the CD anymore, sadly.

Please, I would like any suggestions from you guys. If nothing works, would I be better off buying a fresh new OS cd?

Specs:
DESKTOP
OS: Windows 7 Ultimate x64 Server Pack 1
Graphics Card: nVidia GeForce GTX 550 Ti
Processor: 3.30 gigahertz Intel Core i5-2500K
Drive: ASUS DRW-24B3ST c ATA Device
Board: P67A-GD65 (MS-7681) 2.0
Controllers:
ATA Channel 0 [Controller] (4x)
ATA Channel 1 [Controller] (4x)
Intel(R) 6 Series/C200 Series Chipset Family 2 port Serial ATA Storage Controller - 1C08
Intel(R) 6 Series/C200 Series Chipset Family 4 port Serial ATA Storage Controller - 1C00
Standard Dual Channel PCI IDE Controller (2x)

(i dont know what else to put, but if you need anything else specifically please ask away)

You can also use the installer provided above to do a Repair Install

But first I'd run full Malwarebytes
and SUPERAntiSpyware.com - Downloads full scans.

Then run SFC /SCANNOW Command

These other Troubleshooting Steps for Windows 7 might also help and will teach you more about Win7.

thanks guys! i'll let you know if this works :3 -trying now-

when i try to open the setup it says , the file "sutorun.dll could not be loaded or is corrupted.
It also said "f:/sources/spwizeng cannot run on this version of windows or is corrupted

i burned it correctly thats for sure. And I double-checked my OS and it does say Windows 7 Ultimate 64x .

What are you trying to do? Are you trying to run Setup as Administrator to do a Repair Install? See if Setup will run on another PC to queue up the Repair Install. If not confirm the ISO by size and burn another DVD using ImgBurn at 4x speed.

Try booting the disk to Clean Reinstall - Factory OEM Windows 7 - steps same for retail.

There's a step to rescue files if need be.

You can also work through these steps for Troubleshooting Windows 7 Failure to Start if you'd like to try everything possible to repair Win7 first. If you can't get into Safe Mode to run Malwarebytes I'd run at least one bootable AV scan, then run SFC /SCANNOW Run in Command Prompt at Boot to try to repair system files.