My answer is motivated from your desire to run Ubuntu on the Presario V5305WM.
The V5000 laptop works fine with Ubuntu.
You will probably find hard drive references however, this is a different option.
You have an ExpressCard slot which can take a CompactFlash adapter.
This lets you plug in any Compact Flash memory there and it will go in completely inside the slot
(unlike USB flash drives which stick unsafely out of the laptop frame).
Alternatively, if you are more adventurous -- and, I suggest you don't jump to this yet -- there are also SSD drives.
Once you get this hardware setup, you can install Ubuntu from a LiveCD straight to the memory in this slot and boot from it. That will give you a 'solid-state' memory making your laptop more mobile (the hard disk platters are not very happy with movement and shakes in the back seat of a car or the metro, for example).
Here is one Ubuntuforums discussion on VM5305WM, you will probably find more recent ones.
Here is one reference for Compact Flash memory.
You probably don't need extremely fast cards -- 133x and such should be good enough.
CompactFlash IDE (ATA) emulation speed is usually specified in "x" ratings, e.g. 8x, 20x, 133x. This is the same system used for CD-ROMs and indicates the maximum transfer rate in the form of multiplier of the data rate of an audio CD, which is 150 KB/s.
where R = transfer rate, K = speed rating.
For example, 133x rating means transfer speed of: 133 * 150 kB/s = 19,950 kB/s ~ 20 MB/s.
And, You should look for a good adapter which will not slow-down your access.
I am not too good with the adapter part, some one else here will probably help out.