Before buying a new PC, perhaps we can have a crack at helping you repair the present one.
Please post your problems in the Helproom forum click here.
Assuming you already have a broadband connection, you can add wireless broadband to your present setup by getting a wireless router - e.g. for cable BB click here, or for ADSL BB click here.
If you're not on broadband, some ISPs do a wireless router for no additional cost when you join - some that I know of are O2 & AOL. G