Q:

How do I scan my windows partition for viruses from Ubuntu? 

I think I might have a virus on my windows partition and I want to scan it from Ubuntu.  Is this possible?  I would like a program that is free.  
clamAV 
I tried clamAV but I couldn't find a setting for scaning my other partition that I have windows on, it scaned my Ubuntu disk and that was fine.  
Antivirus Within Windows 
I can't use my Windows partition since the virus make my laptop freeze every time I log in.  And I don't want it to spread or make more damage than it might have done already.  

A:

There is lots of bootable anti virus disks you can use, I would recommend AVG Free.   AVG has over 110 million user.   It provides antivirus protection for Linux/FreeBSD for free.  

AVG Free is a version of the AVG antivirus which is free for private
  and non-commercial use.   There is no graphical interface available for
  the current Linux versions of AVG.1

To download Click here. 

Once you install, reboot the PC to initialize AVG.  Alternatively you
  could run
sudo /etc/init.d/avgd start  

To start using AVG, just press Ctrl+Alt+T on your keyboard to open Terminal.  When it opens, run the command below
sudo avgupdate

Read more
However I would suggest that you run an up to date anti-virus scanner from within your windows partition.   Or you can use Bitdefender.  Boot CD available here
For the top 5 Anti virus for ubuntu.  See here
1Source:Ubuntu Documentations

A:

It is possible to scan your windows partition.  I recommend you do it off a live CD (32 bit). 
Download and install Avast!  Linux Home Edition. 
Launch Avast and update its Database. 
Now mount your Windows Partition. 
Click on Selected folders and browse to your partition. 

Click start scan. 

A:

Install ClamTk - that is a graphical frontend for ClamAV, the command line antivirus mentioned here.