|The short answer....|
You can connect the 4 pins on the PCI USB 2.0 card to ONE front port on the case, if it's the usual situation where each port is / was connected to the pins for one port on the mboard, if the wiring connector(s) coming from the front ports can be plugged into the pins such that the uses for the wires and the pins are compatible with each other.
If the wiring itself supports USB 2.0 use, the front port will work fine with devices that work better with ports that support USB 2.0 specs.
The typical two front case ports located lowest down on a tower desktop case are usually connected individually to the pins on a USB header on the mboard - each port connects to the pins for one port.
The typical pair of front USB ports (or an accessory plate that has 2 or 4 USB ports that installs in a slot space in the case) on a desktop case that connects to a header on the mboard for a pair of USB ports by using wiring that has
- situation 1 - an individual female connector for each wire, 4 or 5 wires for each port - the connectors usually have letters printed on them that are abbreviations of what they are for.
- situation 2 - a pair of 4 or 5 in a row female connectors - usually there are no letters printed on them.
- situation 3 - a single double row female connector, each row of wires being for one of the two ports - common on brand name system cases - usually there are no letters printed on them, and usually one pin hole is blocked so that it can fit on a USB header on the mboard only 1 way.
- situation 4 - an individual female connector for +5v and 1 or 2 ground wires or a ground wire and an overcurrent wire, a female 2 wire connector for +and - data, for each port
If a port has 5 wires for it, either it has
- 2 ground wires, one a ground for the port's power, the other a ground for the outer metal shell of the port
- or - a ground wire for the port's power and an overcurrent wire.
If a row of pins on one side of the double row header, or a single row header, on the mboard has 5 pins, either
- 2 pins are for ground
- or - 1 pin is for ground, another pin is for overcurrent
Which pin is for what on the USB headers on the mboard was never standardized, however,
- a particular mboard brand will usually have the same uses for the pins in the same order and pin arrangement on all their mboards
- as time has gone by, there are fewer mboards that use oddball pin arrangements on the USB headers, so newer mboards of different brands are more likely to have the same for the pins in the same order and pin arrangement on all their mboards.
- if you have a generic system with a retail mboard model, the manual for the specific mboard modelalmost always shows you which pins on the mboard USB header are for what use
-if you have a brand name system, the info about which pins on the USB header on the mboard are for what may or may not be in the support info on the brand name's web site for your specific model. E.g. that info is often there for Dell or HP or Compaq systems in info about the mboard. OR - sometimes, if the mboard is a mboard that is an OEM mboard that has a brand name bios version that is also sold retail with the maker's bios version or that the actual mboard maker has the info about the OEM mboard for, e.g. the mboard was made by Intel, you can consult the mboard manufacturer's manual for the model. OR, there are third party web sites for some brand name systems such as for emachines that know which mboard is in your brand name model and they have the USB header info
Which wire is for what in 4 or 5 in a row or in double row female wiring connectors from the case ports was never standardized, but as time has gone by, they are more likely to have the same order of the uses for the wires in the same places
Situation 1 wiring from the ports - individual female connectors - can connect to any USB header on the mboard.
Situation 2 wiring from the ports - 4 or 5 in a row female connectors - can only connect to USB headers that have pin arrangements and uses for the pins that are compatible with the female connector
Situation 3 wiring from the ports - a single double row female connector that usually has one blocked pin hole
- can only connect to a double row USB header that has uses for the pins and a pin arrangement that is compatible with it
- can connect to a less common single row USB header on one side of the double row connector only if the header has uses for the pins and a pin arrangement that is compatible with it
Situation 4 wiring from the ports - a paired connector for + and - data and individual connectors for everything else - will work with any USB header that has the two pins for data for the same port next to each other.
Your PCI USB 2.0 controller card and most PCI USB 2.0 cards, if they have pins for a port on the card, usually have a standard arrangement of uses for the 4 pins.
+5v on one end, then Data -, then Data +, then ground on the other end.
The colors of the insulation of wires coming from the case ports (or coming from an accessory plate that has 2 or 4 USB ports that installs in a slot space in the case) varies, but usually
- the wire for +5v is red, the wire or two wires for ground or overcurrent is (are) black, the other 2 wires for data are two different colors, or the same color but one has an additional colored stripe -the striped wire is usual for data - .
Only 4 wires need to be connected for an individual USB port - for +5v, ground for the power, and two wires for + and -data.
If 5 wires are connected for a port,
- one of the wires / pins can be for either a second ground or for overcurrent.The intended uses for the wire / pin on both the USB port and the USB header must be the same.
- if both wires / pins are for ground, it doesn't matter which wire or pin for ground you use if you connect only 4 wires
- if the intended uses for the 5th wire / 5th pin on the header are not the same, you can't connect the 5th wire to a pin - your mboard bios will generate a message about overcurrent or similar even when nothing is plugged into the USB port
- if the wiring of a 4 or 5 in a row connector is otherwise compatible with the uses for the pins on a USB header, if the connector from the port has a 5 in a row connector and 5 wires, plug it into the 4 pins in a row on one side of a double row (or single row) USB header so the 5th wire does not connect to a pin; if the connector is 4 in a row / 4 wires, plug it into the 5 pins in a row side of a double row (or single row) USB header so there is no connection to the 5th pin
- if the wiring has a single double row connector,you can't plug it into adouble row USB header unless you can plug into only one side of the header, or unless you cut the 5th wire, or bend metal tabs flat inside the hole in the connector and release it's metal wire end from the double row connector.
Plugging a compatible wiring connector or connectors from one of the case front ports (or from one port in a plate that has 2 or 4 USB ports that installs in a case slot space) will support USB 2.0 use IF AND ONLY IF the wiring between the port and the 4 pins on the PCI USB 2.0 controller card support the minimum requirements for USB 2.0 .
The minimum wire gauge (thickness; diameter; the lower the gauge number the thicker the wire) for USB 2.0 is higher than for USB 1.x, and preferably the wiring from the USB port should have braided wire shielding between the ends around the wires for each port.
If the wiring is not adequate for USB 2.0 use, you will get the nag message from Windows about the device you have plugged in would work better if you plugged it into a USB port that supports USB 2.0, when you plug in something that Windows "knows" would work better if the USB port supported USB 2.0, such as a flash drive, an external hard or optical drive, or an external memory card reader.