Going to attempt to figure it out right now, but yes help wouldn't hurt have never done this before.
is it possible to sync a windows desktop qt client?
Where are you based? I had trouble syncing from the UK but my other systems (In the US) synced fine, first time.
Have you added the nodes detailed below to your client? Do you need help adding them?
addnode=198.205.118.181:4777
addnode=191.101.9.62:4777
addnode=218.24.154.38:4777
addnode=61.235.146.130:4777
addnode=144.76.123.194:4777
addnode=92.222.37.29:4777
addnode=80.74.157.31:4777
But use the above nodes - they are the most current.
If someone has detailed instructions on how to set up a full-node - that'd be extremely helpful as well.
This is something we should have explicated so others can add some too.
Here's my "cheat-sheet" to get a working Datacoin wallet going

Link to Windows wallet -
http://sourceforge.net/projects/datacoin/files/Download datacoin-qt-131204.zip
Unzip it (drag file onto desktop usually does it, or click the unzip icon in the folder)
Run datacoin-qt
After the wallet boots up, you'll notice that it doesn't connect to any active connections.
To fix that, go to the 'Help' tab on the top, then 'Debug window'
The 'Console' tab comes up.
At the bottom of the Console tab you can enter commands to the wallet.
We are going to add nodes. I went through this thread and others and found nodes that may be active.
type the following:
addnode 107.170.165.126 add
then hit return.
I added all of the following using the above command format:
107.170.165.126
108.61.57.85
125.135.114.73
162.243.125.211
198.12.12.83
46.4.147.38
144.76.123.194
80.74.157.31
104.131.69.82
graymines.net:4777
My wallet is now connected to 11 nodes!
Not sure which ones above are active - just know that one or more gets the wallet working

Hope this helps my fellow Datacoin peeps!
And as of today (6/3/2015) the size of Datacoin is about 1.2 gigs. (Bitcoin is currently about 32 gigs)
Peace.