I wanted to try OpenERP v7 on a new windows 8.1 operating system but afters starting it for the first time I am getting this error:

Internal Server Error

{"message": "OpenERP Server Error", "code": 200, "data": {"debug": "Server Traceback (most recent call last):\n File \"C:\\Program Files (x86)\\OpenERP 7.0-20131205-002453\\Server\\server\\openerp\\addons\\web\\session.py\", line 89, in send\n File \"C:\\Program Files (x86)\\OpenERP 7.0-20131205-002453\\Server\\server\\.\\openerp\\netsvc.py\", line 292, in dispatch_rpc\n File \"C:\\Program Files (x86)\\OpenERP 7.0-20131205-002453\\Server\\server\\.\\openerp\\service\\web_services.py\", line 122, in dispatch\n File \"C:\\Program Files (x86)\\OpenERP 7.0-20131205-002453\\Server\\server\\.\\openerp\\service\\web_services.py\", line 359, in exp_list\n File \"C:\\Program Files (x86)\\OpenERP 7.0-20131205-002453\\Server\\server\\.\\openerp\\sql_db.py\", line 484, in cursor\n File \"C:\\Program Files (x86)\\OpenERP 7.0-20131205-002453\\Server\\server\\.\\openerp\\sql_db.py\", line 182, in __init__\n File \"C:\\Program Files (x86)\\OpenERP 7.0-20131205-002453\\Server\\server\\.\\openerp\\sql_db.py\", line 377, in _locked\n File \"C:\\Program Files (x86)\\OpenERP 7.0-20131205-002453\\Server\\server\\.\\openerp\\sql_db.py\", line 440, in borrow\n File \"psycopg2\\__init__.pyc\", line 178, in connect\nOperationalError: could not connect to server: Connection refused (0x0000274D/10061)\n\tIs the server running on host \"localhost\" (::1) and accepting\n\tTCP/IP connections on port 5432?\ncould not connect to server: Connection refused (0x0000274D/10061)\n\tIs the server running on host \"localhost\" (127.0.0.1) and accepting\n\tTCP/IP connections on port 5432?\n\n\nClient Traceback (most recent call last):\n File \"C:\\Program Files (x86)\\OpenERP 7.0-20131205-002453\\Server\\server\\openerp\\addons\\web\\http.py\", line 285, in dispatch\n File \"C:\\Program Files (x86)\\OpenERP 7.0-20131205-002453\\Server\\server\\openerp\\addons\\web\\controllers\\main.py\", line 573, in index\n File \"C:\\Program Files (x86)\\OpenERP 7.0-20131205-002453\\Server\\server\\openerp\\addons\\web\\controllers\\main.py\", line 98, in db_monodb_redirect\n File \"C:\\Program Files (x86)\\OpenERP 7.0-20131205-002453\\Server\\server\\openerp\\addons\\web\\controllers\\main.py\", line 109, in db_redirect\n File \"C:\\Program Files (x86)\\OpenERP 7.0-20131205-002453\\Server\\server\\openerp\\addons\\web\\controllers\\main.py\", line 90, in db_list\n File \"C:\\Program Files (x86)\\OpenERP 7.0-20131205-002453\\Server\\server\\openerp\\addons\\web\\session.py\", line 30, in proxy_method\n File \"C:\\Program Files (x86)\\OpenERP 7.0-20131205-002453\\Server\\server\\openerp\\addons\\web\\session.py\", line 103, in send\nFault: <Fault could not connect to server: Connection refused (0x0000274D/10061)\n\tIs the server running on host \"localhost\" (::1) and accepting\n\tTCP/IP connections on port 5432?\ncould not connect to server: Connection refused (0x0000274D/10061)\n\tIs the server running on host \"localhost\" (127.0.0.1) and accepting\n\tTCP/IP connections on port 5432?\n: 'Traceback (most recent call last):\\n File \"C:\\\\Program Files (x86)\\\\OpenERP 7.0-20131205-002453\\\\Server\\\\server\\\\openerp\\\\addons\\\\web\\\\session.py\", line 89, in send\\n File \"C:\\\\Program Files (x86)\\\\OpenERP 7.0-20131205-002453\\\\Server\\\\server\\\\.\\\\openerp\\\\netsvc.py\", line 292, in dispatch_rpc\\n File \"C:\\\\Program Files (x86)\\\\OpenERP 7.0-20131205-002453\\\\Server\\\\server\\\\.\\\\openerp\\\\service\\\\web_services.py\", line 122, in dispatch\\n File \"C:\\\\Program Files (x86)\\\\OpenERP 7.0-20131205-002453\\\\Server\\\\server\\\\.\\\\openerp\\\\service\\\\web_services.py\", line 359, in exp_list\\n File \"C:\\\\Program Files (x86)\\\\OpenERP 7.0-20131205-002453\\\\Server\\\\server\\\\.\\\\openerp\\\\sql_db.py\", line 484, in cursor\\n File \"C:\\\\Program Files (x86)\\\\OpenERP 7.0-20131205-002453\\\\Server\\\\server\\\\.\\\\openerp\\\\sql_db.py\", line 182, in __init__\\n File \"C:\\\\Program Files (x86)\\\\OpenERP 7.0-20131205-002453\\\\Server\\\\server\\\\.\\\\openerp\\\\sql_db.py\", line 377, in _locked\\n File \"C:\\\\Program Files (x86)\\\\OpenERP 7.0-20131205-002453\\\\Server\\\\server\\\\.\\\\openerp\\\\sql_db.py\", line 440, in borrow\\n File \"psycopg2\\\\__init__.pyc\", line 178, in connect\\nOperationalError: could not connect to server: Connection refused (0x0000274D/10061)\\n\\tIs the server running on host \"localhost\" (::1) and accepting\\n\\tTCP/IP connections on port 5432?\\ncould not connect to server: Connection refused (0x0000274D/10061)\\n\\tIs the server running on host \"localhost\" (127.0.0.1) and accepting\\n\\tTCP/IP connections on port 5432?\\n\\n'>\n", "fault_code": "could not connect to server: Connection refused (0x0000274D/10061)\n\tIs the server running on host \"localhost\" (::1) and accepting\n\tTCP/IP connections on port 5432?\ncould not connect to server: Connection refused (0x0000274D/10061)\n\tIs the server running on host \"localhost\" (127.0.0.1) and accepting\n\tTCP/IP connections on port 5432?\n", "type": "server_exception"}}

Any idea why and how can I overcome this?

Thanks in advance for your reply.