starting simple:
Have you downloaded and installed java?
if yes:
when have you last updated it? It might or might not update automatically
If it's old, just uninstall it and download 64 bit java only. 99% of time you have no use for 32 bit java. (only reason to use it is if for some reason, your windows is still 32 bit)
if no:
are you using latest minecraft launcher that should automatically download java for it's own use.
Another possibility is of course that for some reason too aggressive firewall/anti-virus is blocking java from running as security issues about java are.. well.. common. (this is far less likely than problems with above yes/no questions)