As you say you want to spend at least 7 days getting there/touring around, the best bet would be and Inter Rail global pass. This is not as good as it was 20 years ago when most trains were walk-on. Since the advent of market pricing on trains, nowadays you have to get reservations for European high speed trains and all (I think!) remaining overnight trains in western Europe have global fares. Thus you have to buy supplementary reservations etc over and above the purchase price of the Inter Rail, so it is not as simple to just rove around Europe as it once was.
Having said that, if you choose your trains carefully and you choose the leisurely option, you can do it. For example there are still the Brussels Strasbourg Basel /Chur locomotive hauled trains which are remnants of the traditional Europe wide network of non high speed loco hauled trains.
Personally I would recommend trundling through France or Belgium/Germany then tootling round Switzerland or Austria before moving on to Italy.
In Switzerland, all trains are walk on although you would be restricted to the railways that accept Inter Rail (some private lines and mountain railways dont accept Inter rail without a supplement). Many trains in Austria are also walk on. The advantage of these two countries (apart from the obvious mountainous scenery) is their manageable size which allows you to do lots of the different lines at a leisurely pace.
As Lou says, do buy a Cooks European Timetable and a Rail map of Europe. (I used to work for the former and hand drew the original drafts of the latter
)
If you want detailed gen on real trains join the specialist European groups: European rail Yahoo group (just read the postings strictly a no questions gen site), and its sister group European-railway-discussion (where you can ask as many questions as you wish on any European railway subject.)
The routes of least resistance ie where you would not compulsorily have to pay a speed supplement or a reservation fee are:
(A) via Brussels and Basel
Eurostar to Brussels
Eurocity Iris/Vauban (depending on time of day) to Basel or beyond, perhaps breaking the journey in Strasbourg (some diesel hauled suburban services, expanding tram network and very good culturally)
(B) Via Paris and ordinary trains (not TGV)
Eurostar to Paris
Paris Est Mulhouse behind a big CC72100 CoCo diesel (see separate post on this subject) and maybe see Alsace for a couple of days
Or
Ordinary trains Paris Bercy Dijon, then Dijon Lyon or Grenoble, then perhaps go Lyon Chamonix Martigny (scenic international narrow gauge past the foot of Mont Blanc) to get into Switzerland.
One way to find out if your long distance journey is supplement-free is top go to the Bahn.de (aka Hafas) European journey planner. Click on Follow this link:
Look in the point to point journey planner left hand side and look for further search options. In the journeyplanner window that pops up you should see an option to search all without ICE, or advanced selection means for transport. Both of these ways will allow you to deselect high speed trains (ICE is the German high speed train), so selecting this option means you will get all an itinerary using traditional non-high speed trains, but sadly you cannot deselect night trains. However, Once you get a detailed itinerary up, you can play around with the length of stopover at specific places to force, for example, an overnight or 2-night stay.
Using Hafas you can demand zig zag itineraries such as the one I have tried here, namely Brussels Firenze via Nurnberg and Interlaken
