installing guest additions to kubuntu guest

[mIXpRo]

hii all ,
i've installed kubuntu 10.04 on a sun virtualbox , and when i tried to install the guest additions i got this error in the terminal :
Building the VirtualBox Guest Additions kernel modules .... fail !
(Your system does not seem to be set up to build kernel modules.
Look at /var/log/vboxadd-install.log to find out what went wrong)

i'am running windows 7 as a host operating system .

[mIXpRo]

doesn't matter , it was a silly problem (gcc isn't installed).
i went to /var/log/vboxadd-install.log
and saw it written there .