For general all-round usage, and occasional/general Photoshop use, you don't need to configure a high specification computer. As I don't know your budget, I'm going to assume around £500, for which I can recommend the specification below:
Case STYLISH PIANO BLACK FUSION CASE inc. 2 FRONT USB Processor (CPU) Intel® Core™i3-540 Dual Core (3.06GHz, 4MB Cache) + HD Graphics Motherboard ASUS® P7H55-M SI: MICRO ATX VALUE MAINBOARD,USB 2.0 & SATA 3.0Gb/s Memory (RAM) 4GB SAMSUNG DDR3 DUAL-DDR3 1333MHz (2 X 2GB) Graphics Card INTEGRATED INTEL HD GRAPHICS (HDMI, DVI, 1920 X 1200) Memory - 1st Hard Disk 500GB SERIAL ATA 3-Gb/s HARD DRIVE WITH 8MB CACHE (7,200rpm) 1st DVD/BLU-RAY Drive 24x DUAL LAYER DVD WRITER ±R/±RW/RAM Memory Card Reader INTERNAL 52 IN 1 CARD READER (READS XD, MS, CF, SD, etc) Power Supply & Case Cooling 350W Dual Rail PSU + 120mm Case Fan Processor Cooling INTEL SOCKET LGA1156 STANDARD CPU COOLER Sound Card ONBOARD 6 CHANNEL (5.1) HIGH DEF AUDIO (AS STANDARD) Network Facilities ONBOARD 10/100/1000 GIGABIT LAN PORT USB Options 6 x USB 2.0 PORTS @ BACK PANEL (MIN 2 FRONT PORTS) AS STANDARD Operating System Genuine Windows 7 Home Premium 64 Bit - inc DVD & Licence (£79) Office Software FREE Microsoft® Office Starter 2010 (Limited functionality Word & Excel) Anti-Virus BULLGUARD INTERNET SECURITY - FREE 90 DAY TRIAL Warranty 3 Year Standard Warranty (1 Month Collect & Return, 1 Year Parts, 3 Year Labour) Delivery STANDARD INSURED DELIVERY TO UK MAINLAND (MON-FRI) Build Time Standard Build - Approximately 8 to 10 working days
If you use Photoshop intensively, I would recommend a dedicated graphics card rather than integrated graphics.