Help

I have some problems in my laptop

1. My computer when purchased(6 months ago) was quite fast....but now it is very slow

2.Windows automatic update is not working

3.When i did a System Health scan (windows tool)

it gave warnings- a)System is experiencing excessive paging

b) Avg. Disk Queue Length : mean - 8, minimum-2, total-16

I am also planning to reformat my laptop..but i'm confused to install winxp or vista

Please help.

My computer information -

OS Name    Microsoft® Windows Vista™ Home Basic
Version    6.0.6000 Build 6000
Other OS Description     Not Available
OS Manufacturer    Microsoft Corporation
System Name    WORKGROUP
System Manufacturer    Dell Inc.
System Model    Inspiron 1520
System Type    X86-based PC
Processor    Intel(R) Core(TM)2 Duo CPU     T5250  @ 1.50GHz, 1500 Mhz, 2 Core(s), 2 Logical Processor(s)
BIOS Version/Date    Dell Inc. A03, 16-08-2007
SMBIOS Version    2.4
Windows Directory    C:\Windows
System Directory    C:\Windows\system32
Boot Device    \Device\HarddiskVolume3
Locale    India
Hardware Abstraction Layer    Version = "6.0.6000.16407"
User Name    WORKGROUP\fanta
Time Zone    India Standard Time
Total Physical Memory    1,013.57 MB
Available Physical Memory    140.35 MB
Total Virtual Memory    2.22 GB
Available Virtual Memory    796.14 MB
Page File Space    1.28 GB
Page File    C:\pagefile.sys