As the popup is part of windows telling you something has crashed, the short answer is you aren't. But if you post much more information, ie what operating system are you using, what hardware have you got and what program is crashing ? Somebody may be able to come up with some suggestions. First off run scan disk and defrag the PC.
Well - seeing as he said a pop up and not the blue screen of death (Windows 95-2000 ;) ) - on would guess it's windows XP.
So, if it's that - it usually asks you to send the error report to Microsoft - to get rid of that do the following:
Open Control Panel Click on Preformance and Maintenance. Click on System. Then click on the Advanced tab Click on the error reporting button on the bottom of the windows. Select Disable error reporting. Click OK.
deviecoops yet again not really enough info for anybody to work with, try running the command msconfig in the run window and then list all the programs in startup in this posting. Some of them may be causing problems.