Quote - hello,
I have a acer aspire 3103WLMi notebook and am running out of room...told i had 2mb of free space...NOT GOOD!

Indeed NOT GOOD, anything less than 5 Gb is too little.

Quote - Now i have been told that yes you can install and run programs from an external hd but it's not advisable...why is this...does anyone run poser from an external hd?

You can install any program on an external HD but it will be slow. A lot programs will only load portions of the executable in memory and load anything required on demand. As all external drives are always slower than anything internal this means a lot of delay in running the program. Also keep in mind that many shared components (DLL's) are always loaded in the Windows directory (so always on the internal drive). In general it is best to install all programs always on the internal drive.

Quote - Also i am unsure of what to get my hd is 60GB PATA HDD is this something i need to match? I see a lot of External HD with SATA but not PATA can i use SATA ? Does it matter?
I don't know much about technical hardware stuff so any help would really be appreciated.
Thanks in advance

One option would be to replace the internal drive. Regardless of the information of the manufacturer this is always an option, a 60 Gb internal drive is small nowadays and could be replaced with a larger drive at minimal cost (you will need to find somebody capable of copying the existing drive to your new drive). In general notebooks do not expose PATA (parallel connection, used only for internal drives) or eSATA (SATA is a serial connection used for internal drives, eSATA is the external drive connection) connectors so you will have to get a USB drive. You will have to check if your notebook have USB 1 or USB 2 connections (same connector but difference in speed) not all external drives can handle USB 1 connections.
Contact your local supplier (not one of the big stores). It may be cheaper to replace the internal drive (with copying and man hours) than getting an external drive. When you get another internal drive don't forget about a backup solution, so you may need to buy an external drive anyway for backing up your internal drive.