Repeater?

Should I get a repeater? I have a wireless router in my office, but my kids say upstairs the signal isn't that good. If so, what type of repeater? I know nothing about this kind of stuff.

Tech Support Guy System Info Utility version 1.0.0.2
OS Version: Microsoft Windows 7 Home Premium, Service Pack 1, 64 bit
Processor: AMD Phenom(tm) II X4 830 Processor, AMD64 Family 16 Model 4 Stepping 3
Processor Count: 4
RAM: 7927 Mb
Graphics Card: ATI Radeon HD 4200, 256 Mb
Hard Drives: C: Total - 940150 MB, Free - 249657 MB; D: Total - 13420 MB, Free - 1617 MB;
Motherboard: FOXCONN, 2A92
Antivirus: Ad-Aware Antivirus, Updated and Enabled