The following link to the homepage of Klagenfurt (http://www.info.klagenfurt.at/inhalt/501.htm), gives the possibility to search hotels and locate them via GIS-Klagenfurt. The distance to the university is given in walking minutes (F). If there is no appropriate public transport available you will find the mark "(PKW)".
Furthermore you can find also hotels around lake Wörthersee with more or less optimal connections via public transport.

Hotel	Category	Distance to University
Hotel Dermuth Urlaubs- und Seminarhotel	****	20min F, suburban
Hotel Sandwirth	****	45min F, City
Arcotel Moser Verdino	****	45min F, City
Hotel Rokohof Business-Seminarhotel	****	25min F,
Hotel Goldener Brunnen	****	50min F, City
Hotel Blumenstöckl	***	50min F, City
Hotel Plattenwirt	***	15min F, near University
Hotel Rösch	***	30min F, near lake (PKW)
Austria Classic Hotel Weidenhof	***	35min F, near lake (PKW)
Schlosshotel Wörthersee	***	25min F, near University
Waidmannsdorfer Hof	***	20min F, suburban
Hotel - Fischgasthof Jerolitsch	***	35min F, near lake (PKW)
Pension Wachau	***	15min F, near University
Cityhotel Zum Domplatz	**	45min F, City
Gasthof Müller	**	20min F, suburban (PKW)
Jugendgästehaus Klagenfurt	Youth hostel	10min F, near University
Volkshilfe Mozartheim	Students residence	15min F