Processor - Single-core = no-no now-a-days. What a multi-core processor does is when one ''core'' gets hot, it'll switch to another one. Dual-core is great for personal uses, Quad-Core if you're running a server.
RAM - What superMarket said. You want DDR2 or higher because DDR2 can work at 5.3GB of bandwidth a second. You don't want DDR holding your processor back, do you? (:
OS - XP is still currently the best, imo. Even better than 7.
Hard Drive - Not really that small, compared to other stuff out there, sure. But let's think about it. Average game is only a couple gigs. Biggest games I've seen was in the 15GB and that's WoW and Aion, the 15$ a month games. You don't need excessive amounts.
Graphics Card - Pretty good, 512 can get you into most games for now
So, it's a decent deal but with the kinda stuff that's on there right now, it sounds like it's an older model of PCs and it's not going to upgrade well when you want to upgrade.
Also, if you want to compare prices to under-the-market prices, you can go to
Tiger Direct