OS Name Microsoft Windows XP Professional
Version 5.1.2600 Service Pack 3 Build 2600
OS Manufacturer Microsoft Corporation
System Manufacturer Dell Inc.
System Model Inspiron 1520
System Type X86-based PC
Processor x86 Family 6 Model 15 Stepping 13 GenuineIntel ~1995 Mhz
BIOS Version/Date Dell Inc. A08, 4/21/2008
SMBIOS Version 2.4
Boot Device \Device\HarddiskVolume1
Locale United States
Hardware Abstraction Layer Version = "5.1.2600.5512 (xpsp.080413-2111)"
Total Physical Memory 2,048.00 MB
Available Physical Memory 296.60 MB
Total Virtual Memory 2.00 GB
Available Virtual Memory 1.96 GB
Page File Space 3.84 GB
About the only thing you could do is upgrade the RAM, since if Xaanos's specs are right it is a laptop. However, you'd have to get DDR2 SODIMMs, so keep that in mind. More RAM would also only help if you're running out, although it's possible with that amount for modern games.
On the chance that it is a desktop, you might be able to put in a decent graphics card. It would be bottlenecked by the processor, but it could be reused later when you make more upgrades. Keep in mind that Dell computers often have low wattage power supplies, so getting something good would require a new power supply too. That's all if it's a desktop, and I'm pretty sure it isn't.
Not sure how you got all that from the information given, but sure.
About the only thing you could do is upgrade the RAM, since if Xaanos's specs are right it is a laptop.
It is a laptop it gives the model number in the op.
Don't upgrade the laptop it can run most low graphics and older games.
If you want to run more modern games like BF3 you are going to need a whole new computer no amount of upgrading that laptop will let it run that.