Windows 7 unable to connect wirelessly - windows 7 and new acer laptop

[merrittsimon]

i apologise if this seems like a stupid post. i am trying to sort out my new acer laptop (windows 7 home premium) but have a problem with wireless connections. if i am next to the wireless modem then my connection is fine, but as soon as i move more than 4 m away i lose the connection although sometimes it claims to still be able to 'see' the network. this happened with the last modem i had as well. i also have an xp desktop, an HTC phone (runs android) and a mac all of which can connect to this wireless network throughout my house without a problem and have always been able to do so. the wireless signal is strong everywhere i want to use it.
i presume there must be a setting on the acer that needs to be changed?

thanks for any help

Simon

ps
all drivers are up to date