Slow dell inspron 8500

i didn't know were to post this but anyway. I have had major problems with this computer its my dads home pc and it been running very slow for a long time now. It take windows up to 30 mins to load and even then in took me almost 15mins to open opera i cant find the problem or if theres a lot of them were they are and just to make things so much better the wireless network keeps having to be repaired over and over hers all the info iI have

1. computer specs
General
Processor Pentium 4-M

Processor speed 2.4 GHz

Motherboard chipset Intel 845MP
Memory/Storage
Amt of RAM 512 MB (max 2048 MB)

Hard drive 40 GB

Optical drive 24x8x8xCD-RW / 8xDVD-ROM combo drive
Connectivity
Ports 2 x USB 2.0, 1 x IEEE 1394 (FireWire), 1 x serial infrared / IrDA, 1 x serial, 1 x parallel (IEEE 1284), 1 x display / video S-video output

Modem Integrated 56Kbps fax modem (V.92)

Built-in devices 2 x SO DIMM memory slots, 1 x PC Card slot (type I/II)
Display
Graphics hardware Nvidia GeForce 4 4200 Go

Amt of video RAM 64MB

Diagonal screen size 15.4 inch

LCD technology Active matrix TFT

Screen resolution (max) 1680x1050 (up to 1920x1200 for the WUXGA model)
Multimedia
Sound hardware Intel AC'97 audio chipset
Software
Operating system Win XP Home

Software included WordPerfect Productivity Pack (includes options such as MS Office XP, MS Works Suite, etc)
Chassis
Weight w/battery 2.99 kg

Dimensions 361.3 x 276.2 x 38.6 mm
Power Supply
Battery type(s) included 9-cell "smart" Lithium-ion battery (72WHr)
Warranty
Warranty One-year on-site warranty and one-year mail-in service (options to upgrade warranty coverage to three years is also available)

3. network hardware
air plus extreme-G router
network card: D-link airplus DWL-G650
running on DSL
thats it if you need mor info i can probely get it

 

it keeps telling me windows can not complete task