reduce size on harddisk

[gth]

I can't download any programs anymore because Outlook takes too much space
(1.8 GB) on my c: disk. Can I reduce that space?
Note: If I try to work offline, I get error messages, so if the idea was to
download all my folders (which are too big anyhow), then that was useless.
The c: disk was installed by my guru; I also have a d: disk with enough
space on it, but they're unable to change those settings.
G. 't H.

 

[DL]

So how large is your C drive?
Where are you seeing 1.8gb for outlook size?
What size is D and is it a separate drive, or simply a partition?
Answers to the above are required before any meaningful advice can be given