Why Is My Desktop Internet Slow?

Could be interference by another access point on the same channel. Of the 11 North American channels only 3 do not overlap any others (1, 6, 11). Virtually everything is defaulted to channel 6 which creates an instant conflict with others. Try switching to either channel 1 or 11 and see if things improve.

How do I change that?

Consult your router's documentation.

If your desktop is only 15 feet from the router why not run an ethernet cable and get top speed , a lot better than wireless.

I tried running it but its not connecting, i can only go through wifi

You may have to diable the wireless adaptor and enable the onboard lan adaptor. Go to the control panel , then network and internet and then network connections and you should see two adaptors one wireless and the other a lan adaptor and you can see if the lan adaptor is enabled or disabled. You can enable the lan adaptor and try it before disableing the wireless adaptor.

I don't see the Ethernet one, I just see the wireless one.

Do you have an ethernet port on the rear I/O panel ? If you do then you have to go into the bios and enable the lan connection and install the drivers from the motherboard cd.

Ethernet is much much faster, not sure why the wlan card is so slow

Are yuo now connected by cable ?

Yup,

Wireless is always slower then wired . but the newer routers are getting faster then the older routers.