Well would you care to tell us what is causing it ?
It isn't just saying that ashServ.exe is using the CPU, what we need to determine is what is the activity it is scanning.
Is this Trend anti-spyware part of a suite ?
Have (or did) you another AV installed in this system, if so what was it and how did you get rid of it ?
Edit:
Vlk, always says that the guidelines for solving of the problem "ashServ.exe using too much CPU" has always been the same:
1. Check if the avast tray icon is spinning (while CPU usage is high)
2. If it is, click it (wait for the dialog box to open), and check which file is being scanned (the Last Scanned field); the Scanned Count value should be increasing (spinning icon means a scan is in progress)
3. Find out which of the providers is scanning the file (click "Details" button and check out the Last Scanned value for each of the providers). The most common providers that may cause this are Standard Shield, P2P Shield and IM Shield.