Basic reference on STOP errors at http://www.aumha.org/a/stop.htm
A system thread generated an exception which the error handler did not catch. There are numerous individual causes
for this problem, including hardware incompatibility, a faulty device driver or system service, or some software issues. Check Event Viewer (EventVwr.msc) for additional information."
If you have access to the XP Recovery Console...I suggest trying to run the chkdsk /r command, as a first step.
Have you tried to run the Dell Diagnostics module?
<<i tried to start windows again using safe mode and it didn't work.>>
Error message? What (exactly) happened when you tried?
Do you have access to another system?