linux partition problem

I let someone else partition my hard drive and add linux, after they installed a new hard drive and windows. I wanted to do it myself (which is the best way to know something has been done, and done properly), but this person took it upon himself to do it (did I mention that he put in the new hard drive without telling me first so I could back up my system? A little annoyed here....). So anyway, the hard drive is supposed to be 20g, but when I check it says its only 2, which leads me to believe he either put the wrong hard drive in, thinking I am a complete moron, or he partitioned way too much to linux and not enough to windows. But, I can't get the mouse to work in linux anyway, so I have no way of checking.
so my question is, does anyone know how I can uninstall linux and delete the partition? Do I have to reformat the whole hard drive?
also, he said that my modem wasnt' compatible with linux, but I didn't see it on the list that I had of incompatible modems, it is an HP modem. If it is incompatible then I won't bother trying to install linux there, I will just get another computer for it. Any help would be greatly appreciated, I haven't been able to get past the word go on this.

The incompatibility of your modem could be due to the fact that it is a "win modem".

Do you use Win9X?
-> you can check the partition size by entering fdisk in dos... start your pc when it tries to load Windows press F8 to get in the startup menu -> choose DOS -> type in the dos prompt fdisk. It will ask about large disk support press yes, choose view partition information, look at the info.
there is a primary partition if you have several partitions on 1 drive there will be an extended partition too, with other logical partitions in it.

It will show your drives, partitions, volume labels, size and the file type:
for the linux partition(s) it will say NonDOs partition.
Look at the amount of total space. It has to be something like 20024MB for a 20GB disk...

Its one of those modem/sound card deals that only HP seems to have, ofcourse, the computer came with Win98.
Thanks, for the info.