it could be a whole bunch of things.... first off, what components are old/new..... need more info, so we can help.....

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My PC:
AMD 1700+ 1.47 @ 2.16 180fsb
ABIT kx7-333r
Kingmax 512mb DDR400
ASUS gf3 Ti200 64mb
LiteON 522452 CDRW
WD 80gb se IBM 40gb
SB Live 5.1 Creative 5.1 spkrs
Lian-li pc60usb
Enermax 350watt
Logitech dual optical mouse
Samsung 955df 19'
cable 1.5mbit down 190kbit up