can you press ctrl + alt + del to bring up task manager in regular mode
then if you have explorer.exe showing in the process list, end it
then go to file, new task and type in explorer.exe
does your taskbar come back now??
Have you done a system restore to a point where you had a taskbar??
have you insured your pc is clean and no infections??
what is your current antivirus, and what scanners do you have installed??
do the following: (you might have to do it in safemode with networking:
Download, install, update and do full scan with these free malware detection programs:
Malwarebytes Free (MBAM):
http://www.malwarebytes.org/products/
SUPERAntiSpyware: (SAS):
http://www.superantispyware.com/
Remove all found, reboot, and run again until scans run clean, these can be removed afterwards if you so choose. Run scans one at a time, please.