As already mentioned, RAM (Random Access Memory) and storage space (space on your hard drive) are two different things. If you have 750 gigs of something, you're talking about storage space. No home computer has 750 gigs of memory (RAM).
Which were you running out of on your former PC? Could have been either. If it was storage space, I doubt you'd have to worry about it for a good long while if you've got a 750 gig hard drive, unless you're doing some serious high res photography, videography, etc., and lots of it. But if for some unknown reason your hard drive was created with a small partition for the C: drive, it could happen even if your physical drive is huge. That's unlikely, I would think, but could be resolved by reconfiguring the drive.
If it's RAM, on the other hand, easily handled - eliminate startup programs you don't need, possibly increase virtual memory or add more RAM. Virtual memory is a lot slower than RAM, so if it came to that, adding RAM would be preferable, but adding virtual memory is free (just change a setting and reboot).
What operating system do you have? I'm assuming it's Windows something.
