Windows 7 - Restoring Outlook after total HD failure (following windows 7 udates)

After windows 7 updates last wed I had to reinstall windows 7 (64bit) as system restore wouldn't work. I now want to restore my outlook 2010 to its original state. My hard drive was backed up to a cloud storage company and I am now downloading my outlook files. There are around 10 files ending in .pst and another 4 in the form archive1.pst etc.

My question is - can I merge all the into one outlook.pst file and one archive file? If not how do I know which is the most recent one?

I guess you backed up & exported the pst. at the same day? if you don't remember, in that case you have to import all and select (do not import duplicates)
and yes, once you imported all pst. files in your outlook, the next time you export them again - they will get saved all in one pst.

The Livedrive program automatically backs up the pst files. Do I use import then? People in the past have advised against this and said to use 'open'.

I'm not sure of how livedrive works.
but to import the Pst. files on outlook:-
1) click File on the top left corner
2) click on Import & Export and select Import from another program or file
3) scroll down and select Personal Folder File (.pst) then click next
4) now from browse navigate to where your .pst files are saved. select and click open., you will get three options for "duplicates" select which you need and click next.

But which of the dozen or more pst's and can I merge them into one?

yes, once you import all your .pst files in your inbox the next time you export them, they will automatically be exported to one .pst file.

please check the most recent date (Date Modified) ,for example. look at my .pst files you can see the most recent date is 14th Jan and older are like 03rd Jan