I play poker on a netbook and I have no problems with its speed whatsoever.
I have ASUS EeePC 1005P Intel Atom N450 1.66Hz Processor, 1Gb RAM, Win7 Starter edition. Hard drive size has very little to do with speed. Poker software does not require high specs PC. Your internet connection is more important.
I can run 3 different poker site
clients with a couple of tables open on each at the same time with no probs.
I can also run FTP with Holdem Manager and play at 4 tables. I don't play more than 4 tables but if you want I can try to open more tables and see how it goes.
The only problem (not really, I got used to it) is a small screen. You won't be able to tile tables, but if you cascade or stack them you should be able to play them easily.