Since you haven't been on the internet, you can rule out spyware, trojans/virus's (assuming you haven't shared something)
Here's a couple simple things to check first:
Reboot and immediately tap the F8 key about once per second, you'll come to the 'startup screen where you can select 'safe mode.' Select it using your up and down arrow keys, and hit enter,
Once you're in safe mode, go to start>programs>accessories>system tools>
SCANDISK
When it opens, check it to run in the 'thorough mode' and Check to fix errors 'automatically'
See if you can get through that, it will take a long time, an hour maybe more,
Post back any error messages,
If it fails, try it in the 'Standard' mode,
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After that while still in the 'safe mode' go back to;
start>programs>accessories>system tools>
Disk Degragmenter
Start the program, it will also take a long time to finish,
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Now click on Start / Run /
Msinfo32
When the program opens, click on 'Tools' , then click 'Registry Checker' , let it run and see if the registry checks out ok, or if it is 'successfully repaired'
While still in ' microsoft system information' look in the left pane and click the +sign for 'Components', scroll down and highlight 'Problem Devices' .......look in the right pane, are any problems listed?? Look for 'this device has a problem' in red,
You can also back that check up by going to 'device manager' ,
Right click on your 'my computer' desktop icon, then select 'properties' , then 'device manager' ,,,, look for any yellow exclamation marks, post any details,
reboot your computer and test .......
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If all of this fails to boot normally, use your 'system restore'
Boot back into safe mode again,
go to start>programs>accessories>system tools>system restore
Select a 'date' before this problem started , enter, then reboot when prompted, and test,
If you can't even get to the safe mode, you can use your 'emergency boot disk' to do all the above, but first try 'safe mode'
