If you are using your HTC dire first time then you have to configure Wi-Fi on the HTC desire to connect the internet, you had to need some extra steps to make Wireless works. You can connect to Wi-Fi using following steps.
Select Menu from the home screen. Find Settings, select Wireless & networks.
A list of Wi-Fi network will be displayed on the screen.
Select the desire network to connect. If the wireless network is secured with WEP then enter the key and click Connect button
Select the Wi-Fi check box to turn Wi-Fi on.
Now your phone is connected to the wireless network. Wi-Fi icon will be displayed in the status bar.
Note: If you have problem connecting to internet, provide static IP and DNS will resolved your problem.
If you are trying to reset, updated rom and you will get the following error message.
flg=0x10200000 cmp=com.android.settings/.wifi.WifiSettings bnds=[124,404][236,531] }
D/SettingsWifiEnabler( 548): Received wifi state changed from Enabling to Unknown
W/SyncAllWidget( 151): activeSynch is null false
I/ActivityManager( 79): Displayed activity com.android.settings/.wifi.WifiSettings: 495 ms (total 495 ms)
I/WifiHW ( 79): wifi_load_driver enter
D/SettingsWifiEnabler( 548): Received wifi state changed from Unknown to Enabling
D/dalvikvm( 1805): GC freed 3806 objects / 257536 bytes in 97ms
D/NetworkLocationProvider( 79): onCellLocationChanged [1363,22890]
I/WifiHW ( 79): wifi_load_driver end error 2
E/WifiService( 79): Failed to load Wi-Fi driver.
D/SettingsWifiEnabler( 548): Received wifi state changed from Enabling to Unknown
Use Static IP will also fix your problem.
How to setup Static IP
To do this, Apply following steps.
Open your WI-FI from Menu->Settings.
Click advanced bottom, enter your static IP.