I would like to connect a anemometer(RS-485, DB9) to the PC. The PC has a serial port with DB9 connector. I couldn't find the specification of the serial port. Is that RS-232 standard or RS-485? Most commonly used the RS-232, so I assume that is RS-232. Is there a possibility to configure the serial port from RS-232 to RS-485, or I just need a RS-232/RS-485 converter?
An EIA-485 ("RS" refers to "Recommended Standard", and is an obsolete name) interface is rare on a PC, you'll need a separate interface board for that. The reason is that EIA-232 and EIA-485 are not hardware compatible, despite using the same connector type: EIA-232 uses single-ended signals, meaning that RxD and TxD are referenced to ground. EIA-485 uses balanced signals, meaning that both sent and received data have a positive and negative signal which are each other's negative.
PC serial ports are always RS232 (originally designed for use with modems). You would need a converter, it will not be software configurable because there is different hardware required to drive RS485 lines. You can get PCI cards with RS485 on them eg http://www.brainboxes.com/pci-serial-cards/protocol/RS422-485
As an alternative, you could use a USB to RS485 converter in a lead such as this one.