Getting the pop-up:
MALICIOUS URL BLOCKED
avast! Network Shield has blocked a harmful site.

Object: random url
Infection: URL:Mal
Process C:\Users\Name\AppData\Roaming\dwm.exe

This message is coming up quite frequently (particularly when i initially open my web browser). I have done scans and no viruses were detected. I’m not exactly good with computers btw, and thanks for your time.

Process C:\Users\Name\AppData\Roaming\dwm.exe

upload suspicious file(s) to www.virustotal.com and test with 44 malware scanners
when you have the result, copy the url in the address bar and post it here for us to see

alternative
Jotti http://virusscan.jotti.org/en
VirSCAN http://virscan.org/

follow the guide here http://forum.avast.com/index.php?topic=53253.0 and attache the logs

Lower left corner > additional options > attach
if the logs should be to big, then upload to http://www.mediafire.com/ and post the download link

http://virusscan.jotti.org/en/scanresult/fd8090b216d7b70815059ce4695476bfd435a9c8

searching that MD5 at VirusTotal give this
http://www.virustotal.com/file-scan/report.html?id=da7f0fab5c63ec961d4e0ff5980f1173fbd2a2550662f7e71aff1181b49bd3e3-1315394771

looks like it can be a new bug…and i guess avast want it, so you do this with it

Moving files to the Virus Chest
http://support.avast.com/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=501#idt_03

Submitting files from the Virus Chest to avast! Virus Lab
http://support.avast.com/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=501#idt_07

That is malware - quarantine it and send it to Avast

There may be other hangers on as well

Download OTL to your Desktop

[*]Double click on the icon to run it. Make sure all other windows are closed and to let it run uninterrupted.
[*]Select All Users
[*]Under the Custom Scan box paste this in
netsvcs
%SYSTEMDRIVE%*.exe
/md5start
explorer.exe
winlogon.exe
Userinit.exe
svchost.exe
/md5stop
C:\Windows\assembly\tmp\U /s
CREATERESTOREPOINT

[*]Click the Quick Scan button. Do not change any settings unless otherwise told to do so. The scan wont take long.
[*]When the scan completes, it will open two notepad windows. OTL.Txt and Extras.Txt. These are saved in the same location as OTL.
[*]Post both logs