XP Pro Won't Boot - System Services files corrupted? How To Repair/Restore

Boot problems with an IBM Thinkpad X41 running XP Pro SP2. XP starts as normal, and I can log in as user. But it never finishes setting up the desktop - it populates the desktop with icons, but doesn't finish applying the icon pictures to them - about half of them remain as generic icons - and it doesn't get any further than this. The Start->All Programs list opens as a blank white window, the cursor goes to an hour glass, and the machine is unusable, it just won't do anything.

If I use the MSCONFIG utility to do a "Selective Startup" with "Load System Services" unchecked, the machine starts up fine (but without USB, network, internet access, etc. of course) but if I check "Load System Services" the boot hangs as I described before. I guess this means that one or more of the "System Services" files are corrupted.

I have tried restoring to "last known good configuration" and also using the System Restore utility to roll back to a couple of previous System Checkpoints, but it appears that these don't restore the System Services files as it doesn't fix the problem.

I am guessing that "last known good configuration" and System Checkpoints only record vital settings, whereas the problem I have seems to be that one of the System Services files on the hard disk has got corrupted, so restoring previous settings does not cure the problem.

How do I go about repairing or restoring the corrupted System Services files?

 

If you boot up you can run System File Checker
Start>Run>sfc /scannow
This may ask for your System Disk (XP install CD)
This will repair all system files to their original state.
Because of this, you will have to download all new Security Updates from MS