Syncing multiple iOS devices with the same iTunes installation on Windows 7
There shouldn't be a problem with this at all. Simply connect the devices and set them up as normal. I have an iPod, iPad, and several iPhones that sync with my Mac and I have not encountered any problems.

As far as using different email, contact, and sync info, you can set up all of that on the actual device itself in "Settings" > "Mail, Contacts, Calendars". 

Syncing with iCloud
If you will be syncing email, contacts, and calendars using iCloud on each device, be sure to uncheck the following in the "Info" tab in iTunes:

-"Sync Address Book Contacts"
-"Sync iCal Calendars"
-"Sync Mail Accounts"

Syncing without iCloud, Using Sync Data from Your Mac
If you will be syncing email, contacts, and calendars using the info that is on your Mac, check off the following in the "Info" tab in iTunes, and then select which email account, contact list, and calendars you want to sync:

-"Sync Address Book Contacts"
-"Sync iCal Calendars"
-"Sync Mail Accounts"

Syncing Content from the iTunes Store
As far as syncing audio and video that was purchased from the iTunes Store, you will need to enter the proper account information on each device. This can be done in "Settings" > "Store". Changing the Apple ID in the "Store" settings will not affect the Apple ID used for iCloud.