|"1GB RAM AND18MB hard disk...."|
I'm guessing you meant 18GB HDD. That would be OK for XP, but it's not big enough for Windows 7.
"The swapfile in windows should be at least 1.5 bigger than your ram"
That's an old school recommendation that was never really correct. So you're saying if you have 8GB RAM, you should have a dedicated swap file of 12GB? That's ridiculous. The best method is to just leave it alone & let Windows manage the size.
"if you run ubuntu, you may not need any swap file. But you can only use the computer for simple word processing, and not for browsing the web. That would take up too much RAM for you."
Linux will run decently (depending on the distro) with 1GB RAM & an 18GB HDD. And it will browse the web just fine so I don't know where that comment is coming from? Here's some Ubuntu swap file info, see "How much swap do I need?":