(A) May be apache service starts early than mysql?
And it is simply "no connection" at this time.
You can to try start services separately or change startup order:
1. mysql
2. apache
or
(B) Exclude your C:\\wamp\\www\\sqltest.php
from php.ini
ps
Why WAMP?
Use XAMPP (
http://www.apachefriends.org/) - more stable and multi-platform.