Performance and Diagnostics Problems!!

I'm running this

 

OS Name Microsoft® Windows Vista™ Home Basic
Version 6.0.6000 Build 6000
Other OS Description  Not Available
OS Manufacturer Microsoft Corporation
System Name MY-LAPTOP
System Manufacturer Dell Inc.
System Model Inspiron 1521
System Type X86-based PC
Processor AMD Athlon(tm) 64 X2 Dual-Core Processor TK-55, 1800 Mhz, 2 Core(s), 2 Logical Processor(s)
BIOS Version/Date Dell Inc. A04, 10/30/2007
SMBIOS Version 2.4
Windows Directory C:\Windows
System Directory C:\Windows\system32
Boot Device \Device\HarddiskVolume3
Locale United States
Hardware Abstraction Layer Version = "6.0.6000.16407"
User Name My-Laptop\Kristian
Time Zone Eastern Standard Time
Total Physical Memory 893.39 MB
Available Physical Memory 245.39 MB
Total Virtual Memory 2.00 GB
Available Virtual Memory 682.07 MB
Page File Space 1.17 GB
Page File C:\pagefile.sys

 

And it is very slow, although less than a third of the memory is taken up. It has been having problems since it was first made and still just a few minutes ago!

 

The first event is

Critical 11/10/2006 5:11:16 PM Diagnostics-Performance 100 Boot Performance Monitoring

 

And the newest is

Warning 1/21/2008 3:03:51 PM Diagnostics-Performance 302 Standby Performance Monitoring

 

The total of problems is

1,211

 

I did not even turn on my computer for the first time until

Warning 12/15/2007 8:07:08 PM Diagnostics-Performance 200 Shutdown Performance Monitoring

 

It was shipped on (because above was the event directly after below)

Warning 11/17/2007 1:30:57 PM Diagnostics-Performance 108 Boot Performance Monitoring

 

 

And after all this, when I ran the diagnostics relating to my problems, the tests all passed, yet it restarted uncontrollably a few minutes before (repeated restarts, and unable to shut down).

 

Any help at all is appreciated!!!