You can download Windows XP drivers for your laptop model at the Acer Service & Support website:
Acer Europe - Service & Support, Drivers & Utilities, Downloads, Notebook, Extensa 4420
In particular, you'll find the LAN, WLAN and SMBUS drivers there. Note:
that you yourself need to identify whether you have Broadcom or Atheros integrated wireless and install the correct drive accordingly (if you haven't installed your WLAN driver already).
You can also download and install the latest graphics driver (for integrated ATI Radeon X1250 grapics) if you haven't already done so:
Drivers & Tools | GAME.AMD.COM
I'd also advise installing Service Pack 3 as Lexluethar advised.