In order to launch full scan, please use the Task scheduler.
Windows XP:
Open the Windows task scheduler (Start->Control panel->Assigned tasks). Find the Dr.Web Daily Scan task pre-installed during installation and open it to edit. In the Task tab, check Enabled. In the Schedule tab, specify scan frequency and time you need. Press Ok to apply the settings. Enter user name and password upon the operating system request.
Windows Vista/7:
In order to edit a task pre-installed during the anti-virus installation, right-click on the Dr.Web icon in the notifications area and select Tools->Scheduler. In the next window, select the Drweb Daily Scan task, which is disabled by default. You should enable it (by right-clicking the task and selecting Enable option). In the Triggers tab, edit launch time and frequency.