That's the big question! What are the jumpers for? The support team
from the notebook producer told me that the jumpers might be used to
change the FSB but they didn't really want to tell me - you know, to
take a notebook to pieces yourself is something they are not very
happy about (warranty and things like that).

You are right. I won't spend money on a 2400+ or a new 2600/2800. I
found offers for a Mobile XP 2200+ for about 80 Euros / 75 Dollars and
a Mobile XP 2400+ for 150 Euros / 140 Dollars. So I'll try the cheaper
one...

My current processor offers this speed stepping (that's why I don't
think the jumpers are for multiplier-changes):

Mult Voltage Speed
5x 1.250 V 500 MHz
6x 1.300 V 600 MHz
7x 1.350 V 700 MHz
8x 1.400 V 800 MHz
9x 1.450 V 900 MHz
10x 1.500 V 1000 MHz
12x 1.550 V 1200 MHz

CPU: L1 I Cache: 64K (64 bytes/line), D cache 64K (64 bytes/line)
CPU: L2 Cache: 256K (64 bytes/line)
CPU: AMD mobile AMD Athlon(tm) 4 Processor stepping 02

(cuts from powerNOW! for Linux Kernel 2.5.73)

By the way - the link to your page works from here (Austria)

Greets!
Clemens