Unable to launch any apps (I guess .exe)

My laptop (Sony Vaio / Win 7 Pro 64 bit) began playing up a couple of months ago, occasionally clicking on an icon (eg Firefox, Outlook...) in the taskbar (or from the start menu as well) failed to launch the program. The 'cursor wheel' would spin but then a few seconds later...nothing. A reboot generally fixed it. Over the past couple of months this has got much worse, to the point where now nothing will launch and a reboot doesn't fix it.
In safe mode, all appears to be OK. I am working in safe mode now.
I tried sfc /scannow. No problems reported
I have run virus scans with: G Data, SAS, MBAM, MSE, Spybot. No malware reported.
Before I surrender & reinstall Windows, can anyone suggest a course of action to troubleshoot this?
In the event viewer there are a shedload of errors of various types -typically relating to (1) inability to pick up an IP froDHCP server or (2) Microsoft Security Client OOBE stopped. Dunno if they are relevant or just normal running.

Thanks!

No ideas or troubleshooting tips? Really could do with your help here! I'm out of ideas...

Thx!

Thanks for the input.

Nope, not messed with the registry. Though I guess it could have got messed up some other way - through hw error, SW installs, just generally getting out of shape (gawd that sounds limp...).
But am I right in supposing that Windows can just get messed up over time and the best thing to do might be a re-install?
I'm OK doing a re-install (put aside a day) if that's the best advice... Ta!!!

If you're able to create new working users, I wouldn't worry about doing a reinstall. You'll likely not run across this again (as long as you don't play around with those user registry files and the registry itself -- it may be helpful to adjust your system so that it automatically hides system files).

The following link is for Vista, but you may find it useful (especially regarding any email accounts you may have associated with the corrupt user account):

Fix a corrupted user profile

Although the title mentions "fix" a user profile, it's really just a method of recovery by doing what you've already started. The old corrupt profile gets deleted in the end, it doesn't get "fixed".

The weird thing is that I've since reverted to using my account with admin privileges and it's all working OK again.

I started preparing to create & shift to a new account but tried my original account and, for the past day or so, all has been working just fine.

Odd...

Not sure if I should be pleased or suspicious...