How to upgrade my p4

by buying a (cheap) new pc

The only P4 newegg offers is :
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
for $75. And it is not a significant improvement.

I'm afraid david is partially right. You pretty much need to buy or build another PC.

The higher speed northwood is an 3,2Ghz (and not all the mobos support it). And as they have already told you, it's not a significant improvement.

You can get this configuration by less than 180€:

G.Skill 2x1GB DDR2-1066 F2-8500CL5D-2GBPK 5-5-5-15 2.1V 50€
AMD Athlon II X2 250 2x3,0GHz 2Mb AM3 BOX 60,00 €
GIGABYTE MA785GM-US2H MATX "AMD 785G+SB710" 65,00 €

buy a cheap pc.