Go Start>Run, type in:
sfc /scannow
Click OK.
Have Windows XP CD handy.I was reading the useful information and what not for the forums. I'll post detailed specs of my computer just for the *censored* of it.

Operating System
Windows XP Media Center Edition Service Pack 2 (build 2600)

Processor
2.80 gigahertz AMD Athlon 64 X2 Dual Core
256 kilobyte primary memory cache
2048 kilobyte secondary memory cache

Motherboard
Board: NVIDIA NVIDIA nForce 590 SLI 2
BUS Clock: 201 megahertz
BIOS: Phoenix Technologies, LTD 6.00 PG 09/01/2006

Hard Drive
Hitachi HDT725040VLA360 (400.09 GB)

Drives
LITE-ON DVDRW LH-20A1S
SONY DVD-ROM DDU1615

Memory Modules
2048 Megabytes Installed Memory

Slot 'A0' has 1024 MB
Slot 'A1' has 1024 MB

Controllers
Standard floppy disk controller
NVIDIA MCP55 Serial ATA Controller (3x)
Primary IDE Channel [Controller]
Secondary IDE Channel [Controller]
Standard Dual Channel PCI IDE Controller

Bus Adapters
AXEOB4A3 IDE Controller
MagicISO SCSI Host Controller
Standard Enhanced PCI to USB Host Controller
Standard OpenHCD USB Host Controller

Communications
1394 Net Adapter
802.11g MIMO Wireless PCI Adapter/Cardbus Card

Display
NVIDIA GeForce 8600 GT [Display adapter]
WDE L1975NW [Monitor] (19.1"vis, May 2007)

Multimedia
AVerMedia M780 PCIe NTSC/ATSC Combo TV Tuner (Bridge)
AVerMedia M780 PCIe NTSC/ATSC Combo TV Tuner (Capture)
AVerMedia M780 PCIe NTSC/ATSC Combo TV Tuner (Tuner)
Realtek High Definition Audio

Printer
HP Photosmart C3100 series on USB001

Other Devices
Texas Instruments OHCI Compliant IEEE 1394 Host Controller
HID-compliant consumer control device
HID-compliant device (2x)
USB Human Interface Device (3x)
HID Keyboard Device
HID-compliant mouse
NVIDIA Network Bus Enumerator (2x)
USB Composite Device
USB Root Hub (2x)

Virus Protection
Kaspersky Anti-Virus Version 7.0.1.325windows file protection that you said to do, I did it, it got to the end says to put in cd2 and i did and it keeps saying it's the wrong cd, i have a genuine copy of xp media center edition.

i cancelled the last two files, then it finished, and nothing ELSE came up.Try Repair install.I tried repair install. Two files from the check were still missing. ngen.exe - entry point not found. The procedure entry point GetRequestedRuntimeVersion could not be located in the dynamic link library mscoree.dll And the other had something to do with .NetFramework 2.0.6.6 something, I didnt get a chance to get the rest. Also since the repair my display is way laggy. Should I reinstall my graphix card?
In my opinion, you may be facing Windows reinstall, after reformat.One other thing you could try is to boot into safemode...un-install any .Net frameworks installed from add/ remove programs.
Then boot to regular mode and run the sfc fix Broni suggested above and re-boot again.I just reformatted and re-installed windows not even two WEEKS ago. I'll try removing .netframework and try again.after repair install a huge list of windows updates arrived. none of them would install. doesnt sound good.Get Ultimate Boot CD: http://www.ultimatebootcd.com/, and test your RAM, and hard drive.tried this and updates work now

Re-register the related Windows Update files:

1. Click Start, Run, and input the following commands in the Run textbox: (you can make this simpler by copy/pasting one line at a time, then click OK after each one, then click Start, Run again and repeat with the next command)

regsvr32 wuapi.dll
regsvr32 wuaueng.dll
regsvr32 atl.dll
regsvr32 wucltui.dll
regsvr32 wups.dll
regsvr32 wuaueng1.dll
regsvr32 wucltui.dll
regsvr32 wups.dll
regsvr32 wuweb.dll
regsvr32 wups2.dll
regsvr32 msxml.dll
regsvr32 msxml3.dll
regsvr32 msxml2.dll
regsvr32 qmgr.dll
regsvr32 qmgrprxy.dll

You will RECEIVE a message stating the process succeeded after you input each command.

After that, visit the Windows Update site again.