another problem with another laptop

[Rach1980]

hey all,
firstly i apologise for all these help questions and nothing else.
i desperatly need help with my partners laptop.
the laptop was running really badly and so my brother in law suggested reinstalling vista so we got the disk and start a fresh install
there are 3/4 disks
1)has 82.2gb on it
2)has 9.7gb on it
3)has 0.00gb free of 9.?gb
4)i cant remember exactly.
anyway when it asks you where to install windows and you click (to me the obvious choice) disk 1 it says it cannot be installed on there the only one it will allow it to be installed on is disk 2
so when its all done not much space on there, so when he downloads any programs i suggest downloading it to disk 1 but you you try and install it still installs onto disk 2 and then he gets a pop up message "you are running low on disk space"
my questions are if you dont mind
a)why wont it allow me to install windows onto disk 1?
b)why when you have saved to disk 1 whatever program you download why does it then install onto disk 2?
c)is there any way at all to make windows install on the bigger drive OR to make the bigger disk the default disk for downloading/installing whilst still maintaining the use of windows?
all help/advice greatly appreciated
thanks in advance
rach xxx

[Rach1980]

anyone? please??