Hello for the last month, my Toshiba laptop with Vista has been flashing every 30 seconds and a black window pops up with another box called 16-bit MS-DOS subsystem:

Inside the box it says

C.:/windows/system32\WUAUCLT.exe
the NTVDM CPU has encountered an illegal instruction.
CS:11e9 IP:001e OP:ff ff ff ff ff Choose 'Close' to terminate the application

 I cannot seem to find a fixSo, you're using NTVDM in Windows Vista?  I'm not familiar with NTVDM but some searching yields no indication it was intended to work with Vista.  See http://www.webopedia.com/TERM/N/NTVDM.html

Do you know, for a fact, that NTVDM is supposed to work with Vista? Please tell us what you know about that.

Edit: forgot to write the word not in second sentence.Sorry...no idea what NTVDM is for....all I know is the screen is ANNOYING and when I type and it flashes up...my typing is all ERASED..so i have to work quicklySo, you have no idea why the NTVDM message appears in your system, right?  What protections (firewall, anti-virus, spyware) are you using?  I am using NOD32, Spybot search and DESTROY, Superantispyware and Windows firewall...

MIGHT be more...not sure how to tell...